Tomato seedling help

We have 13 jiffy pots of tomatoes, with 3 seedlings in each pot (insurance in case one or two don't do so well).  The Jiffy Pots are the 4" ones, about 5" tall, so we don't have to re-pot once we thin to one seedling.  We're using ProMix Seedling mix with some worm castings mixed in.  Germination was done using the paper-towel-in-plastic-baggie method and it worked great - I think we got a 99% germination rate.  After potting them into the Jiffy Pots, they started poking through the soil on around May 9th (yes, I know, very late!).  We have two 36" SunBlaster LED Prismatic grow lights side-by-side.  The plants started out at about 6-7" away from the lights, but one plant got a bit bleached by the lights, so I moved them about 12" away and turned off one of the light bars.  I realized that was overkill and turned the second light bar back on again a few days later and also raised the plants back up a few inches.

Our tomato seedlings are growing slowly, not as green as they probably should be, and some are dropping leaves (cotyledons) a bit early.  The plants just seem dry, despite our over-watering.  The dropped leaves didn't droop or show any signs of yellowing, they just broke off at the stem and fell off.  Some seedlings appear to have stopped growing entirely.  I think it's too hot, so we've pointed an AC unit in their direction and I put a thermometer in with them so we can monitor the temperature.  It has been way too hot, apparently.  I read that tomato seedlings grow best around 65°F.  They'd been around 74°F-80°F the majority of the time the past few weeks until we got the AC unit (we didn't get it for this, but it's come in handy for this).  Since then they've been around 65°F-70°F the majority of the time now, past 3 days or so.  It hasn't been much lower than 63-65°F overnight, either.

I've also learned that we were watering too much so have cut back.  Anywhere from 3/4 cup to a full cup of water per pot until the tops and sides of the pots get wet.  but apparently that's been too much since the leaves of most of the plants started to turn yellow.  We've used a tiny bit of extremely diluted organic kelp liquid and some sea minerals off and on (also extremely diluted), probably twice so far.  Mostly just tap water that has sat out for 24hrs to gas off the chlorine.  We mist them with a spray bottle maybe once a day.

Some have grown better than others.  Most just aren't doing all that great, maybe 1" with tiny true leaves.  I'm guessing because of the heat and too much water.  It's also humid around here (avg 70-90% humidity recently).  I read that by week 4 we should have plants with 2 or 3 true leaves and about 3 inches tall.  Some are there, most are not.  2 or 3 pots definitely are, with one doing very well (Prairie Fire tomatoes).  Those ones have two branches with 3-4 true leaves, and they will "close up" their branches together like a venus fly trap as if to say "too much light" or, could also be they are stretching and closing up together because of "not enough light".  I don't know.  It looks a bit odd.  The outside of their stems and leaves are purple, which I read could be a stress response.  One of the plants (Black Strawberry tomatoes) are entirely purple, but I think that is more to do with their genetics than stress since they were that way when they poked through the soil, but I'm not 100% sure.

And lighting has been harder than I thought, as well.  I read up on it and found out that tomatoes need a "DLI" (Daily Light Integral) of around 22-30.  https://growlightmeter.com/calculator/  That means a "PPFD" of around 440 for 15hrs a day.  Well, I can't get a PPFD that high with these lights, oddly.  I used an app on my phone, which is suppoed to be fairly accurate, but I'm not sure if it is - but it's all I got.  Some people told me to "just get florescent shop lights" and that they have success with them - well, these LEDs are brighter and full-spectrum - so you'd think they'd be bright enough to do the job...  The plants are about 9-10" away from the lights, with both light bars on.  I'm hesitant to put them back up at 6" away from the lights for fear of burning / bleaching them again.  I might try to raise them up closer by an inch or so over the next few days.

Anyway, I'm hoping we've got things more or less back on track, but it will just take time to really know.

This is my first time growing tomatoes indoors from seed and I'm excited about it, but I haven't found it to be a simple process.  Just thought I'd share in case anyone has any insight, guidance, or suggestions - I'm all ears.  Thanks.

Wow!  Welcome, Goodtogrow!  I am baffled by your situation, you have done way more research than I have ever done….but still very interesting.  

I would keep detailed notes on what is doing well—you will want to grow that again, or at least know that!  Notes from year to year are super important….

Why do you think they are too hot?  I thought LEDs were pretty heatless?

I have a heating pad and 2 4 foot fluorescent lights in my basement to start stuff—and an Aerogarden for winter, which uses LED….seems similar?  

I had to bail on my seedlings this year and go with grower raised plants.  Too cold here.  Nothing was growing?  

Photos would greatly help!

Thanks, SR.  Definitely a good point about the notes.  I am trying to take some as best I can.  I've been trying to do research only because I'm such a newbie to gardening, so I have a long ways to go, unlike so many of you!

The LEDs are very low heat, you're right, but they are more intense - or so I've read, so they can apparently burn/bleach plants fairly easily.  It was only one pot, and only two plants in that one pot that were affected, but I got worried they were all too close.  The centre part of their cotyledons started to go a bit lighter in colour, and it just got worse from one day to the next, so I moved them.  That's what prompted me to look into "PPFD" and "DLI" and all that stuff.  Bit of a headache, but I think I understand it now.  Not entirely sure if my readings are accurate, but it seems to have improved our setup.

I'll try to get some photos uploaded.

Well I went to a local garden centre and was told that it's actually warm enough to put them outside.  So we started hardening them off yesterday, even though some are still only 1" tall.  The person there told me she has tomato seedlings growing in her garden that she didn't even plant, and they're doing fine.  It's been wetter than normal here this Spring.  Which means a lot of rain.  The thing I've realized, too, is that grow lights are mainly for starting tomatoes indoors during the months of Feb-Apr.  So I think it's safe to start getting them conditioned for the outdoors.  Going to keep them out of the elements for now, though, and bring them in at night.  Plus they'll get all the other benefits of being outside like better light, air, and ambient moisture.  We'll see how it goes.