Hi. It looks like an over-watering/drainage problem. Let the soil dry out between waterings. Stick your finger in the soil and, if it's still damp, don't water. Only water if the soil is dry. Tomato plants don't like continuous moisture and soggy roots. Plus, too much moisture can lead to other problems with seedlings, like damping off.

Back of leaf picture here This post was edited by ash1970 on Fri, Jun 6, 14 at 15:40

If you can wipe some of it off, it is most likely mealybugs. If not, let us know if you are east or west. Different insects/diseases affect different climates.

"I forgot to line the bottom with rocks to allow a good drainage (this is my first time growing anything)." Good! Container grown plants don't need drainage substrate in the bottom, and in fact, don't want it. In every growing medium, in the ground, and in potted plantings, there is a level at which the soil's "wicking" ability to suck water upward (think about a paper towel dipped in water) balances the downward gravitational pull. This is called the perched water table. Below the perched water table, the soil is saturated with water, which can suffocate plant roots and encourage root rot. Above this level is usable soil. By adding a gravel substrate, instead of increasing drainage, you're actually moving the perched water table UP in the container, so the plant has even less room to grow. In other words, skip the rocks. Article that explains perched water tables (Link corrected) As for whether or not your growing medium is appropriate for containers.... maybe. Your leaves look like the typical overwatered tomato plant, one that has roots that are water logged or drowning. There just isn't enough information about the product on Lowe's site to say for sure, but I did find other sites that list the product as OMRI certified, but that still doesn't tell us how the stuff acts in the bottom of a large container. You might ask over in the Container Gardening Forum, surely someone has used it and can give some feedback on the results. I searched but didn't find any information on it, so you probably need to ask. "Also, when you say leggy, what exactly does that mean, just stretched out trying to get some sun?" Yes, that is exactly what that means. The "cure" is ample sunlight. Eight hours or more per day is best, although they can get by on six hours. Betsy Note: Corrected Link for Article on perched water tables Here is a link that might be useful: Container Gardening Forum This post was edited by bets on Sat, Jun 8, 13 at 10:32