My plants aren't growing?

I am new to SFG but not new to gardening. I built my first box this year, filled it according to directions, and planted peas, lettuce, radishes, broccoli and carrots the second week of March (which is correct according to my zone, I'm in 6a). They did great at first...but now they are barely growing. My pea plants (snow peas) are maybe 5 inches tall, the lettuce is two inches tall. The radishes are nice and tall (probably 4-5 inches) but they aren't forming bulbs.

The weather was super warm in March and has cooled off to more typical spring temps since then. Could that be the problem?

I gave everything a sprinkle of worm castings today thinking maybe the compost I got wasn't good enough? I had mushroom, cow, earthworm and generic "compost" from Home Depot. I know...that's only 4. There was no way I could spend a fortune on compost, I wish I could but I'm on a super tight budget. As it was, what I bought came out of the grocery budget, I truly didn't have another $20 at that point and I couldn't find another source of cheap compost. I have blood meal left from a few years ago and wood ashes, I could buy a bag of bone meal and do the fertilizer mix from the old SFG book if that might help (I have both books). Or I could maybe get some "good" compost and top dress?

Suggestions?

I planted radishes in my fall garden and what you described is the same thing that happened to mine. I sprinkled a light layer of wood ash on the garden and after that the radishes started to develop bulbs. Just remember that it is very easy to add more ash if you need to but it can be difficult to remove if you add too much.

I would give it a bit of time. You may just need the soil temps to go up a bit more for things to take off. Another thing to try would be to give them some compost tea. As you have compost it would be little effort and cost to make up a batch to give them.

My gardens here in PA are basically in slow motion right now due to the cold spell. They will take off when it gets warmer.

Based upon my personal experience last year, you may have too little nitrogen. I, too, used some generic "compost" from Lowe's last year, and found that it contained lots of bark and wood chips. Both of those suck up nitrogen out of your mix and lend very little nutrition. It may have also had peat moss in it, which also throws your MM ratio off and adds no nutritional value.

Consider some judicious use of blood meal. My garden didn't do very well last year until I did that, and it made a big difference. Use of a broad-spectrum fertilizer may get you through this season, too, until you get the MM balanced.

In the meantime, start up your own compost pile/bin and start looking for sources of various manures to add to it. Homegrown compost can be an inexpensive yet excellent way to beef up the nutrients in your MM as you add the finished product to your garden over time.

additionally, the length of daylight hours also plays a roll in bulbing radish root.
http://gardening.about.com/od/problemspests/tp/Radish-Growing-Problems.htm

Thanks everyone! I'll try sprinkling some wood ash and bone meal, it's not like it can hurt and I have plenty. I'm also going to try to get some really good compost for when I need to add scoops after harvesting. I did wonder about the quality of HD compost, but I didn't have a lot of options. Hopefully it's just the weather, it was in the high 70's the last two weeks of March and then the temps dropped a good 20 degrees.

I need to figure out a place to start a good compost pile, once I have compost of my own I'm sure it will help a lot.