I have 3 rows of potatoes, 1 row of Yukon Gold, 2 rows of New potatoes. I live in SW Georgia. Put them in the ground 3rd week of February, and they were thriving until about a week ago. Leaves started yellowing and getting black spots on them. I tried putting some diatomaceous earth on them yesterday. Today they look awful, going down fast! The plants are actually shriveling up and dying. Help!! What do I do? It's been pretty hot, and the predicted rain didn't come today so now I have the sprinkler on them. Ideas anyone?