im with gt,6.5 is my sweet spot in soil,twice in past grows i have had to swing it to 6.8,,6.3 is your low in soil,,let me ask how old those plants are? have you checked the hannah chart to see were you need to be at this stage,with the red stems i would also say your running cold in there,,i dont ph nothing,when i start i start with 6.8 soil and roll wit it,i dont feed nutrients either,i feed with barley malt,steel cut oats,oat bran,aleo vera coconut water,then i switch it up by using KNF methods with OHN and FPJ,then i switch it up again with extreme blend,my favorite weapon if i have problems and usally dont because,i like to use humic and fulvic acid with the barley malt,,even bottle nutes work great when applied right,there is no this is the best,cause you can cram kriptonite down the plant throat and it only gonna take what it needs,keep this in mind though,them leaves might be twisted and all crazy on ya,but as long as them leaves stay green you gonna have buds and thats what it about,lmao