Where are they currently - inside or out? In a different position from where they were all winter?

they have been in my frontporch--only watered them once a month or so over winter but have been watering when soil dry lately re warm weather

Might pay you to check them out for vine weevil. One of my smaller overwintered ones did well initially then started to fail. Dug it out of the pot......little or no root left. Others OK. One next to it had a massive root and no leaves.....2 large caterpillars had munched the leaves and were dozing on the fleece sleeve. Vine weevil =armillotox= tiny amount in watering can at intervals or look up on internet and follow dilutions.......smells of gas tar but eco friendly. That's what i'm going to try.

What's probably caused the trouble on the leaves is likely to be the sudden drop in temperatures - March was positively like summer, but April has seen a return to winter temperatures, particularly overnight. Even in the porch,they will have felt that significant change. Check for vine weevil if you think that's a possibility, and also inspect the stems and leaves (backs and fronts) for any sign of infestation or disease.