Trichocentrum leaf drop

[Keysguy]

Help. This is Tricho Ollie Palmer which just in the last couple of days has started dropping its older leaves.

I'm near Key West so humidity is good and the coldest we've been so far is around 65F. I mist daily and soak it good 1-2 times/week. It's just sitting in a net pot with no media. It's location is on south side of screen porch in a spot where it gets bright light from roughly 9-1. Fertilizer is very week 1 time/week 20-20-20 and a monthly Kelpak and quarterly CalMag. Same as everything else. First time this plant has acted like this.

I've noticed some of the older leaves browning from the bottom up yet others that have been shed were completely green. No sign of pests for which it was treated a month ago as well as fungal treatment.

Anyone have a clue as to what might be going on? second pic shows location on porch, bottom right plant.
Sorry they're sideways. I didn't run them through my usual app first.

[estación seca]

Those are older leaves. The plant looks otherwise very healthy. I don't have enough experience with Trichocentrum to answer, but it makes me wonder whether this is how they normally drop leaves.

I would look closely at the leaf bases with a magnifying glass. This is how Cattleyas often drop leaves when boisduval scale is present.

[Dusty Ol' Man]

According to IOSPE the ancestry is listed as Lophiaris. All of the ancestor species are looking for a drier period after blooming. And maybe longer light exposure for the winter. Maybe they are getting too much water? Just an educated guess.

[Arne]

The oldest leaves close to the top of the mount are black at the base. That reminds me of rot on the oldest growths of my Broughtonia species. Broughtonia rots very easily on old mounts where they have been sitting for some years. I have a feeling that Trichocentrum is similar to Broughtonia in this respect. Water sparingly and maybe remount in spring. I would also have used a fungicide.

[Keysguy]

[QUOTE I would also have used a fungicide.[/QUOTE]

I did about a month ago.