I think a once only minor change is OK. Constantly fluctuating levels of PH is a train crash. Stable conditions and more water changes than you think are needed is key. I'm no Discus expert so somebody more knowledgable will give a better answer. I used to breed angels and it was a constant fight to get water parameters right for the incomers but Xwife used to just plop....needless to say hers were the happier fish. (*****)