Whatever this is, it is progressing!!!! nute burn, disease??? help me please

it is only on the fan leaves, starting from the bottom to the top. The only bugs that i have ever found in my room are gnats, and they are gone now cuz i tricked em into thinking diluted bleach was standing water! bwahahaha. works really well. anyways, this started on my strawberry cough clone like 4 weeks ago. a couple other clones had small signs but they went away. i doubt its a disease because this is my best and biggest clone! i just started phing my water but i have been using grow and micro nutes for a month, and just switched them over to bloom, except this plant because this could be nutrients burn. BUT i have no idea. please someone help, it has started showing on the top leaves now so i gotta stop this soon! if you want to see what others have said i posted a couple days ago about this but thought id update as its not going away. but the top bud is starting to look nice! INSPIRATION TO HELP ME SAVE THIS PLANT---->

looked wilted and maybe a tad burnt, too much water

My first instinct would be burn. I actually had a small gnat problem, it lead to root rot and lockout on a couple of my girls. They ended up showing multiple deficincies, and got super limps. After a couple weeks, they are finally starting to bounce back again so that could be a possibility as well. The deficiencies are Once the soil is dry again and ready for water, use the plain stuff. Flushing is extreme, I wouldnt go that far, but definitely let 10-15% of the water run through to clear some of the salts. I do this as regular practice on my plain watering intervals.

ya but i really dont think its the gnats cuz i decimated them with hydrogen peroxide for the larva and bleach water for the flying ones, and then this showed up afterwards. It may be over watering, but i have only been watering them one gallon a week and they dry out at least 2 inches beneath the surface. ill probably flush this one a little for the next watering. is it ok to flush with tap water if ive been dechlorinating recently?

h2o2 in soil? that is killing all that lives in your soil. is that common for soil grows?
I have concentrated on hydro studies up to now.

no it doesnt. its pretty intresting, but basically, if u use it in low enough dosage it can kill root fungus and larva in your soil. also when the molecule breaks down, u get h20, water, and o2, oxygen. but my watering cycle is every other watering i put in h2o2 and the other half i put in nutrients. but like i said, dont use alot cuz it is bad in concentration. like i have a 18 gallon water barrel and i only put like 10 ml per gallon. and like everything else, introduce it slowly.

what percentage hydrogen peroxide are u talking about

3% is what i have.

by the way. this was nitrogen overdose nute burn. i hadnt been phing my water so the plants werent getting much of the nitrogen grow shit i was giving them and it was building up in the soil. when i started phing my water it slowly brought my soil ph down so they could get nutes easier all around..... just in time for budding! so my plants stopped using all that N they had been waiting for and it just raped them. my run off water was a dark orange brown. its all clean now though. haha my plants are very happy about that! and u can tell in the buds