I am not a pro and I am sure one will pop in soon. You have a beautiful big healthy plant. They need more space for root development is my guess. I see a huge stem and a tiny little cup for the roots. You are to be commended for growing such a big seedling. Mighty nice.

I would agree with Janice..........looks like a terrific plant to me but I would think a larger pot (or in ground) is what it needs. When my toms. were that size they looked healthy but I don't seem to get that nice thick stem like you have. I use a grow light close to the seedlings but no fan for air movement. Can you describe your growing techniques that got them to this point? (light.and duration, air circ., temps etc) Thanks,

Harry

Leaf rolling is a form of stress.
In some cases it is due to over watering.

It might be due to excess N. Especially if it is combined with the edges of leaves getting crisp.

AND yes, those cups are way too small for those nice n big plants.

Sey

i'm surprised the cup hasn't split in half.
just like humans, as plants grow they need a larger shoe size.

Thank you all for your diagnosis and advice. Yes, the pots are small, but I didn't realize that might be the reason causing leaves dropping/dying, yellow veins, grey spots etc., especially, some of the plants are still doing OK even in the smaller 8oz cup. I guess it might be the varieties. Some varieties are more sensitive to the pot sizes. Anyhow, I would like to give it a try. Too bad, it is still cold outside and no way for me to transplant them to the ground now. I have to keep them indoor for at least two more weeks maybe. I have ordered some 5.25X5.25X6.5 inch square pots and hopefully, the new pots will solve the problem and last me until placing them to the ground.

@Harry: my grow light set up is very simple and basic. I had explained how I set it up on the post here: (scroll down) http://forums.gardenweb.com/discussions/3567415/2016-contest-hybrid-big-beef?n=89

This is my second year of growing tomatoes. I didn't expect they could grow this big. My seedlings grow much faster and bigger compared to last year. I think the strength of two CFL made a big difference in my tote grow light box. The temperature inside the box is easily above 85F. Some time, I have to leave a gap on the top cover to release some heat from the box. I have the lights on 14-16 hours a day. No ventilation method used. My house is pretty dry with furnace on. Also, I used some diluted liquid fertilizer when watering.

In addition to the above, you need to examine the undersides of the leaves (like the one in the first pic) for insect pests like aphids etc. It can be difficult from photos but it sure looks like aphids in some of the pics.

Dave

Thank you Dave. I have inspected the leaves and soil, I'm very sure there is no insects hurting my seedlings. I'm more tending to believe that the rolling leaves caused by the small cup. I have found an old post that you explained to another gardener who had the similar problem as root bound. http://forums2.gardenweb.com/discussions/2983857/tomato-leaves-curling-under-and-dry-again.

As of today, almost all my seedlings show certain levels of leave curling downwards. I have transplanted three to bigger pots and have to wait my new pots to arrive to transplant additonal. Hope my seedlings can hold on a little longer. Fingers crossed.

I empathize with you, Julia. It's always frustrating when they go from looking great to uh-oh. I'm not sure I'm on board with the diagnosis, though. I would be remiss if I didn't mention I have seen some enormous Bonnie tomatoes, peppers etc. in some real tiny pots that looked very healthy with no sign of disease at Home Depot on Saturdays. In fact, last year I bought a hyssop during a year end clearance that looked gorgeous! At 75% off I couldn't not buy it. I got it home and pulled it out of the pot to transplant it in the garden and much to my surprise the roots had completely, I mean COMPLETELY, engulfed the pot. Anyways, here's hoping it just needs a bigger home. Maybe try some fresh air as well.

I just used potting soil mixed with a little of my compost soil. No chemical fertilizer.