Cattleya leaves turning black
I recently purchased several Cattleyas. As a standard practice, I dunk all new orchids in a solution of Physan 20 and water in the hope that I'm killing anything that may come in with the plants.
After several days, I noticed that leaves on several, but not all, the plants were turning a reddish-purple so I took them out of full sun and gave them some shade. Now, I see that some of the smaller leaves are turning black and some of the pseudobulb sheaths have black splothes. Could this be due to too much sun, using Physan 20, or caused by something elese like a disease or fungas?