New to the board, need advice on miniature and compact cattleyas

[SoCalOrchidGirl]

Hi everyone,

I am new to the board and new to cattleyas. I purchased a few miniature and compact cattleyas from a really nice grower and received the plants last week. The plants are big and are in blooming size and have bloomed before. Currently all 4 are growing new shoots, some are growing multiple shoots when I received them. Only one plant has vigorous new root growth. When I received the plants, I unpotted all of them and took a look at the root system and they weren't bad at all. I also repotted them into fresh bark mediums and watered them since they have been in shipment for 7 days. Today I watered them again and noticed one of the cattleyas had root rot (I haven't had time to check the other 3). I took it out of the medium and noticed all the older roots were rotted, which is odd because I haven't overwatered. It has been a week since I last watered it and the potting mix was dry before I watered it today. Now I am wondering if I should have changed the potting mix at all. Will this affect the growth of the new shoots and flowering? Did I somehow screwed up? I heard that cattleyas are expecially sensitive to being repotted. Any advice would be great!