The reddening of the tail can because by ammonia have for check for it I have kept my comet for over 12 years I have never had any issues related to pH your more likely to have problems trying to alter your pH with chemical water treatments also do you use a water dechlorinator like prime when doing water changes at certain times of the year they flush the pipes with high levels of chloramines unless your testing before every water change you could miss it that can cause reddening