Adding pH lowering chemicals is never a good idea for that very reason. Discus need stability in their water chemistry and the constant down-up, down-up you get with the addition of chemicals is bad for them.
Folks here with pH in the 8's keep discus without a problem. The only reason most of us lower it is if we want to breed since hard water makes the egg shells so hard that the babies can't escape to become wigglers. In that case we use RO water or filtered rain water to lower the pH.