My mother-in-law had always had successful vegetable crops. However this year, she has a hard time on those tomato plants. Somehow their leaves are all curled up. They don't look dry; I touched them to feel if they are brittle from drying out. But they are all feel normal. She has years of experience growing vegetables, and I believe that she knows how much to water them....
She said that the tomatoes grow very slowly this time.
What might be the cause for this problem? How to fix it? Thanks.