I have a couple of small orchids, that had never been "fed" since I got them a few years ago, but had bloomed a couple of times in that period. A couple of months ago, I rescued a bigger orchid from my mother's rental property (the tenants thought they were doing a good deed by repotting it in regular potting soil and burying all the roots... accckkk!)

When I brought the bigger orchid to a florist to have it repotted correctly, I also bought some "orchid food". I mixed it according to directions, and watered all three plants with it a couple of times.

The leaves on my smaller orchids turned reddish all along the edges, and the tips looked almost burnt. The larger orchid got a brownish/black spot on a leaf. From the only info I've been able to find online, it sounds like they're getting sunburned, but the smaller orchids have been in the same windows for 4+ yrs

Is the orchid food the problem? Should I move them to another place if I continue feeding them? (Or should I just leave them where they've always been and not feed them again?)

Thanks!!