I planted my first garden this year. I transplanted my zucchini's (grown from seeds) outside 2 days ago after a week of hardening off. The edges of the oldest leaves are turning a brown/gray color and curling in. I did notice this happening while the plants were inside a tiny but, but didn't appear to be anything to worry about. But after transplanting them, the rate of curling and changing color has accelerated greatly. I tried to do some research but I am having trouble figuring out what it may be. Anyone have any ideas and/or how to resolve the issue?