Pathogen growing on lower leaves. Please help

Hello. So I started to notice these black spots some time ago during veg. I assumed they were nutrient deficiencies but I was wrong.

Now im week 3 in flower and on the underside on my plants I have leaves that get those blacks spots soon curl, wither, and die. I don't think it is PM but I could be wrong. In the past I haven't seem PM act like this. I do believe this started from poor airflow and I made it worse with some poor defoilation. New room and first run.

Any help identifying and hopefully eradicating would really appreciated. Peace

I would think if you cleaned up the under canopy growth - it would help with trapped moisture ( leaf on leaf ) and air flow ( no stagnant areas )

That is def the plan. Going to defoliate tomorrow.

Looks a lot like bugs to me. You have the same damage on the top of the plant?

Little black spots is usually bug shit. Damage looks a lot like bugs to me too, any small white spots on the underside of the leaves? Spots under the leaves will confirm its bugs sucking the juice out of the leaves.

Definitely defoliate, that should hopefully help with your issue. Bugs absolutely love the bottom half of the plant when it isn't properly defoliated,

Just like buddha said above, locks in moisture and makes airflow next to impossible. Resulting in stagnant conditions that bugs absolutely love to breed in.

What are your watering practices like? The damage looks a lot like gnats to me, and they're so small it would explain why you're not seeing many. Gnats thrive in anaerobic soil conditions, and their larvae munch on the roots. This is why you see "phantom deficiencies" with gnats, because they munch on roots, and anaerobic soil usually have an acidic pH.

Pretty good rule of thumb, if you can ever visually see a bug (even just one or two), you have bugs in your grow. Period.

Sucks you're in flower now, week 3 is the last time I do any cleaning up of the undercanopy to avoid stressing the plant in flower. Clean what you can, but don't go overboard or you'll risk stressing your plants at this stage of growth.

Just do your best, and chock this up to lesson learned. In the future, a good rule of thumb is to have the bottom 1/3 of the plant completely bare.

All the best.