probably 15 and 20 full frames of
> bees, respectively.

If a Lang has 15-20 full frames of bees now and does what you describe I 
would guess swarmed and then robbed. 
The one could have been queenless.

also:

Full of mites (hence the brood issues) .

part of issue? Nosema ceranae levels?

Bees have been brooding ( raising varroa) since early spring. Commercial 
beekeepers are seeing varroa issues they would normally see next month.

What type of varroa control was used (if any)? Last fall?

formic & thymol work poorly with a screen like you describe.

bee do fine hanging in trees and completely enclosed in Africa in logs.
I do not see the TBH as the issue.

Hope the above helps.

Please tell us what the inspector has to say.

bob

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