Well bonbon all i have ever heard or read is that acidic Ph is bad for your plants and that too much acid will cause the plants leaves to turn yellow. I have never actaully done a hydroponic system though i have grown aeroponics which i assumed was close. Sorry for the bad assumption but now im looking on where exaclty i am wrong when i am i like to know why. So ive been looking up what you said and cant find anything off the basis of what you said im still just reading 6.5-7. If you have a link or anything Id like to see it.