Calcium/Magnesium deficiency?

[Johndeaux22]

I have a couple of Cattleya hybrids that have recently lost new growths. Initially I thought it was fungal or bacterial infection, however after further investigation, I don’t believe this to be the case. I fertilize with nearly every watering with K-lite at 25PPM, in the summer this is 3-4 times a week, in the winter it is 2-3, everything is grown indoors under lights or on window sills. Water source is RO, that typically measures at 10-15ppm. I suspect calcium deficiency, as well as magnesium deficiency on some plants.

I’m not sure whether I need to supplement with cal/mag, or if it’s possible I need to flush with plain RO water a couple of times to get the plants in the mood to take up what is present in the fertilizer. All of the plants in question are grown in either plain medium grade Orchiata, or a mixture of LECA/coconut croutons/orchiata. A majority of my collection is having no trouble at all. The plants in question are in more than one growing area, so I don’t believe cultural conditions are necessarily to blame.