Repotting cattleyas

[Dani8]

Hi, I have a few cattleyas that have been in leca/seramis mix the last few years. I like that I can easily water from above and I don't have to worry about the media breaking down, but I think it's collected salts and the plants are just not doing great. My tap water is softened through adding salts and only 6 months ago I switched to ro water.

The shelf they were on fell yesterday due to a storm and since most of them ended out of their pots, I want to repot them but I'm not sure what to use this time. I live in a cold climate and they are indoors from October till may.

What would you recommend as potting media considering I have ~30 orchids and don't have the possibility of dunking them in water every week or flushing with ro water regularly.