Never have really, I've ran 6 grows without issue and now she wants to be a prissy girl because she's in a grow comp. I gave her a shot of cal/mag with the feed today, I may just try some epsom with the next round if it doesn't straighten out.
Another reason I don't check pH is because I do not own a pH pen. Last time I tried to use the gh liquid type I couldn't get a good reading due to the change in water color when nutrients added.