Hey how's it going? Going off the information provided it could be a few things causing the yellowing. Just as too much or not enough light can cause yellowing seedling plants, too much or too little water or fertilizer could also be the problem. If the soil around your plants has been completely dried out between waterings, your seedlings are probably just thirsty. Overwatering, however, is a very common cause of sickly plants. Let the soil begin to dry a bit between waterings. If you’re watering every day, you may very well be doing too much. If water and light don’t seem to be the problem, you should think about fertilizer. Seedlings don’t necessarily need fertilizer so early in their lives, so if you’ve been applying it regularly, that may be the problem. Minerals from fertilizer can build up very quickly in seedlings’ small containers, effectively strangling the plants. If you’ve applied a lot of fertilizer and can see white deposits around the drainage holes, flush the plant gradually with water and don’t apply any more fertilizer. Good luck.