derek's 90g build, red deer

Would anyone know why my toad stool always closes up for a week or so, then re open. Same with my colt coral. All the other coral in my system look great and are doing well. Have checked all my prams.

Nitrite 0.1
Nitrate 0
PH 8.2
Alkalinity 10
Cal 350
mag 1050
Phosphates is a little high 2.0
I would love to figure out how to keep everything at par.
like my mag, Alkalinity, Cal. cause I have at least 5 gallons of water evaporate every 2 days. and I think that is why I can not keep everything in check. Any ideas on this mater would be of great help.
Thanks.