What Diseases Can Attack Small Seedlings (tomatoe) Indoors Under Grow Lights?

Question

I have 5 Roma Tomatoe plants (Roma) that are about 4 weeks old and the leaves are curling up and under and the under sides are purple with some light spots. I believe it may be the soil, even though it is a purchased seed starting mix. I started cherry tomatoes at the same time and they are just fine. However these Roma seedlings appear to have the same disease I battled last year when they were outside and 4′ tall. I thought they had been bit by a leaf hopper. So now I don’t know if it is the soil or bad seeds which are organic heirloom seeds. What do you recommend I do?

Answer 1

It could be too much fertilizer or too much or not enough water. Purple leaves can be caused by a lack of phosphorus in the soil. These articles should help. This first article talks about the same problems you have and low pH is suspected, which is preventing nutrient uptake, particularly phosphorus.

https://extension.umaine.edu/gardening/2024/05/01/why-are-my-tomato-seedlings-drooping-and-the-leaves-curling/

https://www.gardeningknowhow.com/edible/vegetables/tomato/physiological-leaf-roll-in-tomato.htm

https://www.gardeningknowhow.com/plant-problems/environmental/leaves-turning-reddish-purple.htm