I run my hydro 5.4-5.9 and my soil at 6.5-7.0...No higher than 7.0...that is the high side...above 7.0 and the ph level won't allow uptake of key nutes n-p-k...but also as LOCNAR stated...if they look good, leave them alone...It is good that you ask and don't take info for granted. I sometimes raise/lower ph in order to have plant uptake a particular nutrient; as slight changes in ph create optimum conditions for each nutrient...latewood