Opinions? Is this powdery mildew or something else?

So checked my plants today and got nice and close after a good defoliation session and I noticed some white patches on a couple of leaves, could this be the start of white powdery mildew or is it nothing. I’m in a dwc, 35 gallon, air temps fluctuate between 73-76, humidity right around 50, I have a tower fan on full blast oscillate hitting the sides of the tent and gently breezing the leaves. I did just go 2 month veg without any defoliation so perhaps the leaves got too bushy, I tried to wipe it away with a damp paper towel but it seemed to dry and appear again. Any ideas? Lemme know if I’m missing any info, I doubt bugs I haven’t seen any, last time I saw one it was a fungus gnat about 3 weeks ago and I did a res change and mosquito dunk and haven’t seen one since.

Also doubt it would be an issue, but the res changes are pretty well contained so I doubt any solution would splash them, plus these leaves are higher up on the plant.

I think that's mildew. If you have some low strength hydrogen peroxide on a cotton tip, should do the trick.
Here is some more info:

Here is a good video about exhaust ventilation:

Yeah that’s what I was thinking, I have a prettt good ventilation system, I have a 6 inch ac infinity taking air outside and an active intake fan taking in cooler air at the bottom. Any budget good solutions to fix this, on growweedeasy their solutions I like but also ranges almost 50 dollars for 12 ounces, damn near highway robbery.