Morning Glories: sweet potato vine problem, 1 by MrJohn

MrJohn wrote:
We transplanted several of these into a very large pot at the school garden a month or so ago. They are all pale yellow like the ones in the center of this photo which I borrowed from another Dave's subscriber. They aren't growing much and a few leaves have actually turned brown and crisp.

They are in total sunshine in the middle of a playground. They get watered regularly, maybe too much sometime. But being in the large clay pot, I wonder if they are drying out sometimes - is lack of water the problem? Also, they are planted in a compost mixture that originally was 90% oak leaves - too acidic?

Too much water?
Not enough water?
Too much heat and sun? (mid to high 90s everyday)
Soil to acidic?