Hello all,

I am looking for some help identifying these little black spots that appear on some of my citrus plants. The plants that show these little black spots on the underside of leaves are a few Meyer lemon and Persian lime trees. I've also noticed tiny microscopic reddish bugs (squish them and looks like little blood trail) on some of the leaves of all the plants (with and without black spotted leaves). The black spots seem embedded in the leaves and I can't scrap them off and don't think they are a bugs. Not sure what it is but the trees that have this problem have significant dieback and the leaves that remain are mostly pointing downwards.

Additional info:
All my plants are inside and in front of bay window in my apartment.
Live in Toronto ontario Canada
Plants were inside all summer
Watered regularly
Fertilizer every few months (30-10-10) water soluble solution
Had/have fungus gnat problem entire summer and still have some now
Temp in my apartment is 22c-26c all year (72-78 f)
Affected plants still flower albeit much less and produce fruit.
My more recent plants are potted in sand/peat media and the Meyer lemons and limes in potting soil and some sand
Affected plants are roughly 3-4 years old

Pictures below