Whats wrong with my fish ??

[janalta]

It looks to me like your filefish has a bacterial infection....presumably the same one your dead female brought in.
I assume you don't have an isolation/QT tank for him?

Your tank is still cycling and besides all of the imbalances in ammonia, nitrates, phosphates, etc....there just aren't enough beneficial bacteria and fauna in your tank yet to sustain the critters you've got in there.

I wouldn't do a full 50% water change right now...your fish are too stressed already. Try 25% tomorrow, then give it some time before you change more...testing every day.
PH is the least of your worries right now...I wouldn't worry about doing anything about that until you get your tank stabilized.