I water everyday in hot weather! Most of my Cattleyas are in medium to large grade orchiata.

To continue the above helpful discussion, a particularly stark divide has emerged in a group of Phals that I purchased nearly three years ago. Some were in moss and some in bark. Three got repotted, partly because I thought it would be good for my watering schedule to have all in the same medium. Three didn't, including two in moss and one in bark. The three that weren't repotted are doing splendidly... bloomed for a couple of years and are now reblooming on big, branched spikes. The leaves look magnificent, too, and most roots remain in the medium. The three I repotted look horrible: they have lost most leaves, bloom on shorter spikes with fewer blossoms than when purchased, and they have a lot of roots out of the pots. I use orchiata over a limestone base, MSU-RO 1 tsp per gallon weekly alternating with my usual RO water, they also get monthly Kelpmax 1 tbsp per gallon. So care is identical, age is identical, I use the same potting techniques as I have for nearly 20 years, they grow outdoors in summer and under a 400 watt HID lamp in winter where it's a bit cool but humidity remains around 60.... no difference except the repotting. What's wrong?

I believe you are poisoning your plants. It could be from calcium, but I suspect it is a general situation.

First of all 1 tsp/gal of MSU RO is about 175 ppm N. Personally, I'd not exceed 75 applied weekly, and I know a lot of folks who say 50 is the max.

Add to that the fact that Orchiata doesn't absorb well and dries rapidly. That means that you're probably concentrating the residues in the potting medium quite rapidly.

Add to that the dolomite used in the production of Orchiata, and your solution ion concentration is probably though the roof every time you water.