Blistering leaves, can’t see any bugs any idea?

[PT Brad]

My plants are week 2 of flower.
One of them started getting this blistering and dying leaves.
Growing in Promix, 3 gallon fabric pot
600 hps dimmed to 75%
70 degrees with lights on
45% humidity (using humidifier)
Water when pots are light around every 5 days
Using general organically nutrients
I can not see any bugs with scope and it is spreading
I am wondering if it is some sort of fungas being spread by my humidifier so I turned it off

please help

 

[Chris Scorpio]

Looks like bugs, but Also looks like wind burn/tear

Fan blowing on it?

Nute splash

 

[PT Brad]

I have a fan on low but plants way out of the way are getting it as well
Is a 60x scope enough to see Russet Mites etc?
I have had spider mites on past grows and sure it’s not that.

I was previously not PHing my nutrients as per GO directions but it was down to like 5.4 so I am now going to adjust to 6.5
But no previous grows did this so I can’t see it being PH now?

 

[Chris Scorpio]

I've never had critters, do can't help there

 

[buzz62]

Do you have a pix of the underside? I would trim off any fans leaves that show that and dispose them. I agree with the humidifier off, in fact I really don't think pot plants ever need humidifying if the soil is kept moist enough, and it will eliminate most mildew, bud rot, and mold issues. Do you have circulating fans moving the air/plants constantly? This will also help control mold and mildew, and will make the plants grow faster due to the fresh Co2. My rooms are usually around 30% at their lowest in the winter and I don't seem to have any problems. It does swing around widely when I soak the plants however. I would run ph at 6.0 or so.
Curious why you would run the light at 75%? A 600 HPS is no where as bright as the sun and a flowering plant will produce more weed under more light. Before I switched to full LED's I ran a 600 HPS and 400 watts of LED's in 15 sq feet at about 18" from the plants and they did great.

 

[PT Brad]

I have a fan exhausting the room slowly 24/7 which keeps my co2 ppm around 600.
I have my light dimmed down because I was wanting to eliminate the too much light possibility.
It is very dry where I live and without the humidifier it gets down to like 25% but I would love to not have to use it so I’ll give it a try...
I’ll edit this post with an underside pic shortly

 

[buzz62]

That ones a puzzle as to what is doing that, I have been using hydro style 2 part mixes from Emerald Harvest and Advanced Nutrients, and have never had a nutrient related issue other than going to hot and seeing tip burn. How hot is your nute mix? While its dry here, my room during the grow stays pretty humid especially late veg / early flower, when each large plant drinks 5 gallons a week and I end up exhausting that outside. I do run a humidifier filled with RO water on the entire room at about 40%, so it never drops much lower than that, despite the -35C outside. Gotta love the prairies!
Your new growth looks ok, you may want to remove all the large fans anyway to let light in to the lower buds, and it may contain or slow down what ever that is.