Could you possibly post a photo? And tell us your location too please.

There are so many possibilities based on your description alone that its almost impossible to begin guessing at the cause.

The pellets have so many problems associated with them, windows are never enough light, weak stems and leaf curls can be from too little light, pests, water, nutrients, etc. Over-watering can lead to damp-off, a fungus disease. The possible issues are unlimited.

They make 10-15 different mixes but none of them contain soil as far as I know. Need to know the specific name of the mix you are using. Have you fed the plants anything?

Dave

hey, thanks for the reply. I'm in southern Ontario (Ottawa valley) I haven't fed them anything just kept them generally moist the whole time, I had a few dry out to rock hard and die on me before transplant. The mix called pro mix premium veg and herb mix with myco active / feeds for 3 months. And that's my problem in first place having a hard time finding out if I'm over or under watering or if something else is at work? They've had fans constantly blowing in the room (not direct). The cups have holes in the bottom so water will drip out if I give them too much water. 

I use the ProMix potting soil and it is fine for starting seeds. I think the biggest problem is not enough light. I never had much luck growing seedlings in front of a window, the growlights are on for 16 hours a day and they never get leggy like what is pictured...I also just plant my seeds in reused plastic cell packs or plastic pots...haven't heard much good about jiffy pellets or peat pots, to be honest.

Agree with that the biggest issue is obviously not enough light. Those are some leggy seedlings.

I'm in ON too and was able to build a dual adjustable grow light for $100 at home depot/Canadian Tire. it's a good investment and simple to build even with limited experience. A commercially bought grow light setup kit go for +200

after a closer look at your setup you could just buy the lights and hang them from each layer of your rack.

Oh my those poor things are so light starved! When you get long lanky leggy stems like that the plants circulatory system is badly compromised. Thus the symptoms with the leaves and long term survival is questionable.

Do you really plant to keep and use so many plants? They need to be transplanted deep into cups burying all that bare stem right up to below the leaves. New roots will form all along the stem and strengthen them. But if you can't get them outside or get them much more light they will just turn weak and leggy again.

It really is almost impossible to grow healthy transplants with only window light. A sunroom or greenhouse works, even a covered porch can. But not just a window. There simply isn't enough intensity or sprectrum.

Dave

Update: it ended up being that they were over watered. After about a week of not giving them anything they perked up and the newer growth leaves are straight and not pointing down. The plants behind my sad tomato in the pic are actually watermelon, should have clarified that.

Thanks for all the replies. I'm sure I'll be back a few times throughout my garden to get some tips from the long time gardeners.