Calcium Deficiency on Cattleyas

[amys]

Hi, this is my first post here, although I've been a member for a couple years. I'm not exactly a beginner with orchids, but I'm far from an expert. Also, I wasn't sure which forum to post this question.

Can anyone help with this? Attached is a screenshot from St. Augustine Orchid Society, but this is my problem with 2 kinds of Cattleyas, while other types are doing well. SAOS says this is a calcium deficiency. This has been going on for a couple years, but I thought it was a fungus problem until I found the SAOS article. The fungicide seasonal regiment from Dr. Martin Motes' books that I follow has made no difference, and now I know why.
I live in SW Florida and have been regularly using Peter's 15-5-15 CalMag fertilizer for several years. The west coast of Florida has water that is highly alkaline, so Dr. Motes recommends this fertilizer. I use tap water and Hozon's Siphon Mixer and fertilize my orchids who are mostly on a covered deck approximately once a week in summer or every other week in winter. A couple of them are on trees with the same problem. Seems like my fertilizer should take care of this problem. They have fairly new potting medium. I've gotten advice elsewhere saying I'm using too much fertilizer, but if there's a deficiency, how can I be giving them too much? Any ideas?