[maknwar]

Check you nitrate level. When its too high, your ph can crash. Had it happen to me when I was overstocked and didnt keep up with water changes. Had to change it quite often to get the nitrate down before everything was good. When I have problems, I usually check the basics. Nitrates, nitrite, ammonia, etc... Cloudiness usually means an ammonia spike.

 

[maknwar]

If you have no kh or gh in your tap water, add some sea shells or crushed coral to your filter. That will add some kh and gh. When your kh is 0, your ph will crash.

 

[maknwar]

They will adapt but swings in ph are not good. As long as it stays the same, the fish will be fine.