On some of my peppers ( all of my bacctums) the leaves are curling in to a tall u shape and almost wiliting. I have some of them in a mix mushroom compost, perlite, sand, and jungel growth potting soil, and others in potting soil with a small amount of slow release fertlizer. The ones in the mushroom compost have no fertlizer. They are both in full sun all day long. I water them when the soil looks dry and until water comes out the bottom of the pot. What could be cause of this problem?

Also some of the secondary leaves on the plants are turning yellow and falling off. Is this normal?? Or is somthing causing them to fall off?? Are the two problems related in any way?? Any help would be appreacted.