No one has pointed this out yet here and you most likely know but I will say it anyway, your Ph is what I would consider to be getting on the serious low side. It could be your calibration on your probe if you not calibrated. If you had corals in your tank this would be bad, they would stress and have a hard time building skeleton. Fish less so, but still a stressor to the biology. If you have coral best to keep that low number no less than 8.0 at night. You might want to try one of the above suggestions to bring it up and level it out. It can be frustrating.