Physan 20 help.

[Cattleya17]

Hello! I finally got my hands on two bottles of physan20 and I used it for the first time today. A couple of my plants have shown signs of a leaf rot one seedling phal crown rot and a cattleya and a laelia with leaf rot.

I put the plants out and we had alot of rain here in NY recently and then we had a major cold snap like frost and even snow flurries in a couple if places. I bought the plants in early enough I thought but today I noticed the diseases.

So I mixed two teaspoons of physan20 per gallon and sprayed all of my plants twice (after removing damaged tissue) I sprayed them all because I just want to be safe and I sprayed down the growing area as well. Was this the right move? Mixture? Also how frequently should I spray them?

Also it started off looking like just sunburn. The whole leaf turned purple on the one cattleya then after I bought them inside for the cold snap it faded to only two black spots with a clearish ring around them and they were weeping. Any ideas on what's infected them?