This plant was growing very well. But I had it in normal potting soil. So I transplanted it into a mix of 50% grit, 40% perlite, and 10% potting soil. It's been raining every day so the plant gets splashed a lot but the medium dries fast. I've noticed a lot of leaves are falling off and there are black circles which appear like rot on the leaves. I keep removing them only to wind up with more black circles on leaves. What should I do?