Best advise is not to mess with it. I have discus in a ph of 8.2 and they are doing GREAT! If you mess with PH then you are going to be chasing the PH all day. Unless you are planning on breeding leave the PH alone. If you are trying to breed them then add one or two leaves and let it rest 48-72 hours, then test PH. Then keep adding a few and test again in 48 -72 hours.