First off, take them out of that peat-based mix. They are probably getting root-rot. I grow mine in half potting soil/half perlite in clay pots with 3 inches of pebbles or perlite in the bottom. Drainage is EVERYTHING to a desert rose!

Take them out of the soil, wash as much off the roots as you can, and cut away any rotten roots or rotten spots. Dust the wounds with sulfur. Lay the plant gently on its side indoors and let it dry for at least a week. This won't kill it. It stores water inside, and I've left cuttings curing for months without losing them.

Repot it in a clay pot that is just wide enough for the root system. Mix the potting soil like I said, and put stones or perlite in the bottom. DON'T plug or cover the drainage hole, just put a coffee filter or some screen over it. In fact, I grew a couple in orchid pots with screen covering the holes on the sides and they did great.

The rain won't hurt them if they are up off the ground and planted in soil that drains easily. I always put my pots up on bricks so they could drain.

Since this plant is stressed, after you repot it, don't fertilize it for at least a month. I'd try some SuperThrive to feed it in the meantime. That will get it back to health.

Thanks, dirty. So do you think it is a fungus in the roots? As for sulfur, I have some sulfur crystals but not dust. What is the brand name of the dust?