7 isnt that bad for soil but better would be using 6.5 ph each feeding, watering. Get phosphoric acid and ph meter. Have u measured run off water or PH of soil? Have u used perlite, maybe theres not enough oxygen, which create environemnt for anaerobic bacterias that u dont want.
Do u perhpas have magnifier or pocket microscope of 60x - 100x? U ll need one anyways for trichomes to properly time harvest. With it we could find more about the bug, if its in leaf.
Try to press with fingers the burned place. Althought it doesnt reasemble leaf miner.
Maybe try also tobacco pesticide recipe but dont spray it in buds.
If its a root problem some benefivial bacterias and mycorrhizae could help or hydrogrb peroxide mixed in water but that will kill also benecial bacterias u might have in medium.