health What Are These Leaf Spots?

[Illsstep]

"Facing Heaven" pepper plant (or it's supposed to be).

Black spots appearing on the oldest leaves, none on the new growth.

Spots are entirely interveinal, appear to be recessed, and are followed by an interveinal yellowing of the affected leaves.

Plants are growing indoors under strong lights, in a fast-draining bark-based mix with controlled release fertilizer. Temperatures are kept between 70° and 75° and relative humidity between 55% and 65%. Good air circulation is present.

Any ideas what could be causing this?

 

[Major Pain]

Possible form of BLS? or just the old leaves getting ready to fall off.

 

[Illsstep]

I'm hoping not BLS. The pictures I have found do look similar (but not exactly), but descriptions of BLS also mention the spots starting out as "raised" or "wet looking" spots on the undersides of the leaves. I haven't seen either.

A picture of the whole plant:

It is growing like a weed right now - I'm just worried about the spots, which appear to be spreading.

 

[Major Pain]

Just to be on the safe side, I would remove the spotted leaves and see how the plants behaves for a few days to see if it worsens, or gets better.