Small brown spots on both new and old leaves

[megrower]

Hi! Maine resident here with third legal indoor grow and loving it.

This problem is new to me and perplexing. Pic is from week 5 of flowering, these brown spots started around week 3 and there are more of them as time goes on. The oldest/lower leaves which have the brown spots are starting to yellow as you can see in the pic here. The upper fan leaves which have the small brown spots have a similar pattern (1mm-ish brown spots on main vein / smaller branch veins on fan leaves.) No spots on sugar leaves yet that I can tell.

As the days progress I'm seeing more brown spots on smaller fan leaves towards the main colas as well as these. The older, lower leaves have more brown spots and they're starting to cluster together on those.

Have supplemented with Cal-Mag for 8 days now in case it's calcium deficient, but new spots are still showing up. Tips of leaves are very barely yellow (assuming nutrient burn, but this has never caused brown spots before.)

Fox Farm Ocean Forest soil, Big Bloom/Tiger Bloom nutes. 300W LED light 24" away on 12/12 schedule, supplemental UVB for 30mins per day. UVB is new to this grow but not on a full UVB dose yet.

Soil pH 6.

Any guesses?

[Rwise]

First do a bug check just to make sure, use a 30x zoom lens and look under all the leaves.
The spots say PH/root problem, the yellowing could be normal, how about pics of the whole girl, one leaf doesn't mean a lot to me.
I would raise the PH to 6.5.