Strange spots

Looks like someone with knowledge could identify. Tried searching but haven't come across anything. Initially thought it could be light issue, but it's also affecting leaves lower in plant. Crept up within 10 hours. Only affecting a few leaves, but I'd like to correct asap as this is an auto.

Thoughts?

Provide some info about your grow.
It looks like a pH problem.

MickFoster said:

Provide some info about your grow.
It looks like a pH problem.

Click to expand...

saw that photo earlier but it doesn't seem to be the same. in that photo, the spots go into the middle vein. these spots dont hit any veins, they just sit between the veins.

just soil mixed with perlite. i don't have a ph meter, just pool test strips that show its in range. using advanced nutrients MGB, slightly less than recommended amount.

just noticed the tent hit 104F a few hours ago. not sure what happened there, so maybe that is the issue... oops.