Take some pics with the flash or regular light with the hps off, looks like a
fox farm burn out, I had the same looking plants when I used
fox farm. At some point in their feeding schedule they call for 45ml of nutes total in one gallon of water, that would burn up any plant.
My suggestion is to throw away the feeding schedule after you flush with three times the amount of water as the size of your pot, one gal pot=2gallons of water followed by 1 gallon of correctly Phed water. You can skip the extra 2 gallons if you have a product such as sledge hammer or GH clean because they help rinse the salts away and you could just water them with 2x runoff.
I would pick up a small measuring cup like the ones that come with cough syrup and add only 5ml per gallon of big bloom and tiger bloom each and never go over 7.5ml per gallon each of those two and do the same with the grow big when using it. I would also never go over 20 ml per gallon total of all nutes and additives because I know plants will be really happy with small amounts but not so much if they get just a little too much.