I've had indoor only plants do that with a slight lack of water. Small pots, hot temps could mean the same problem. Bigger pots give you a little more leeway.
When you say the soil seemed moist how deep did you test, though outside today in Northern Ca. it was Hot. Shade sounds like a good next move till you get these back into prime health. If you're using ceramic/clay pots get some damp burlap to wrap them and get the pots out of the direct sun.