Usually when cal goes up, alk goes down. And when alk goes up or down, so does ph. With that said your alk is too low. Raising your alk could/should make ph go up. Which is not what you want to do but alk is to low so start there. When mag is out of range your cal and alk will swing around, and could do weird things like send ph out of whack.
Try to get your cal up closer to 480, and alk at least 8. Do the things I mentioned above about water and air movement, check and if need be adjust your magnesium, and give it a couple of days then re-test ph.
What do you dose with?