Maybe a lack of nutrients; once the true leaves come in they need some fertilizer. I just pot mine up into regular Miracle Gro potting mix, and they get very green and grow big and fast. Haven't noticed any burning using this method. I am hooked on Miracle Gro potting mix, great stuff.

hi, Nope it's perfectly normal you probally have plenty of nutrients in the mix. I personaly wouldn't add nutrients when you pot up wait 2 weeks than hit them with diluted liquid kelp. others will disagree I'm sure and it is probally better to follow their advice.

tomatoes are not heavy feeders they need a wide spectrum of different nutrients but not in large amounts. broccoli is a heavy feeder but not tomatoes.

you might try a diluted calcium boost if you need to feed them something now. you do not need the calcium really, and if you are planting them directly in to the ground not raised beds (when you plant out) unless you have sandy soil you probally have enough callcium anyway. it won't hurt them though so if you feel need to feed, an egg shell soaked in 1 gallon of water will be fine and provide a little extra calcium without burning or harming your seedlings in anyway. just a thought...

I agree, it's normal. The cotyledons usually fall away once the true-leaves start coming in :)

Vera

Great...thanks for all the quick advice everyone.

daylilyfanatic4, I'll keep the calcium in mind. I'm in New England, so I have sandy loam here (and lots of rocks).