Actualy 1 change in pH is 10 times (cuz it's on a log10 system) but your pH is to low, you've over fertilized in some areas and under nuted in others...give up on your babies, if you manage to keep them alive you'll get low yeild of shity bud.. Restart! Don't fert for the first 3 weeks (than go 25%) use true-tone or a marijuana fertilizer. Keep your pH between 6.2-6.8. And the slow growth is not just P def..you've half killed your plant allready, they'd do better without care; sorry but you fucked them up. When this first started you shoulda got help, but it's past hope now. Re start. Try 1 or 2 plants til you can get it right