Calcium Magnesium Questions

[SundayGardener]

Hello,
Thanks to the helpful experienced orchid experts, I discovered that I needed to add cal mag when using distilled water, especially for cattleyas.

I'm able to get RAW Cal Mag locally, but it seems pricey. Searching around, it seems Peters Excel Cal Mag 15-5-15 is popular (but not necessarily easy to get?). My question is, is this used in place of a fertilizer, or in addition to fertilizer? My impression is in place of a fertilizer, in which case, my next questions are is it a good fertilizer for orchids (aside from the cal mag) and should it be avoided for paphs and other calcium sensitive plants? I think I saw in another thread that H&R nurseries uses it, but I believe they grow mainly catts and dens, and species (but not paphs?).

Finally, has anyone ever just used powdered calcium and magnesium? For instance NOW Foods label sells both in a powder as a human supplement.

Then there is the amount. RAW Cal Mag says 1/8 tsp per gallon, but I don't think this is enough for catts. I've seen improvement but still think I see signs of calcium deficiency and I've been supplementing for 6 or 8 weeks now, or longer. I use it for all waterings, although now I'm using up 1/4 tsp for catts and encyclias only.

Thanks for any input! I'd really love to get at least one cattleya bloom this year