My Lemon Boy has been in the ground for about two weeks now and the leafs are turning black around the edges. Could this be a lack of necessary nutrients or would it bee more likely to be a disease. Thankfully it has not spread to my other tomato plants yet but I am worried that it might. My soil has a lot of clay and while I have been trying to improve it the bottom layers of the grow box are still clay. I had to dig down that far because it was such a large plant. Any ideas?

Thank you.

L.G.