Black Spots on Underside of Den. Leaves

[c123anderson]

I have a few dendrobiums that have a weird black spotting on the bottom of some of their leaves. I've included a pic of my Den. spectabile cross as a representative sample.

On the top of the leaves there are few, if any spots; this occurs on the bottom of the leaves.

I have recently posted about my mealybug infestation, which I have treated with insecticidal soap and insecticide (specifically first with tebuconazole, tau-fluvalinate combination then with imidacloprid) and I have also treated with a spray fungicide prior to the insecticide treatment.

The black dots were present before treatments and whatever spread may have been happening seems to have stopped or at least slowed significantly post treatment.

I've scoured the web and orchid board trying to determine what these spots are, since they are predominantly on bottom of the leaves.

Frankly, all, I'm feeling a lot flustered and frustrated with my issues I've had lately. It seemed like problems went from nothing to explosion. Yes, I'm learning a LOT from all of this, and I am sincerely grateful for all the advice here. Hopefully I'm not being hypersensitive now and causing more problems.