I've got 18 one-month-old tomato seedlings growing under lights. They were potted up into 18-oz red solo cups a couple weeks back in Miracle Grow potting mix and up until Saturday have been doing great. I'm growing cherokee purples, pink brandywines and some san marzanos. I've been watering them once a week, thinking that there was no way once a week would be overwatering.
Now I'm wondering if I was wrong. I watered them all Friday night before bed. On Saturday evening, I noticed that one of my brandywines had lost one of its lower leaves. (Not the seed leaves, but a true leaf.) Today I was checking on my tomato plants and noticed that on all of my pink brandywines (And only the brandywines), all of their lower sets of true leaves are turning yellow. The yellow appears to start at the tip of the leaf and move to the stem, where the leaf then drops off.
The rest of the plant and the newer leaves are still green and healthy looking. This all appeared to start the day after I watered them. Could they be overwatered and if so will my brandywines survive?
Also, why would this only be happening to the brandywines? My cherokee purples and san marzanos look green and healthy, and they were watered just as much as the brandywines!
Thanks soo much!