Kh off the charts

[Shawnct]

So I have a 60 gallon with a 30 sump. I've just recently got my first corals and there not doing to well.. I can't seem to figure out the problem. My kh is crazy high
Sg 1.023
Ammonia 0
Nitrite 0
Nitrate 5
Ph 8.2
Phosphate can't tell because I have the api test kit.. not zero but not .25 very slight color change
Calcium 340
Kh 21

 

[John3]

Yeah that is really high, are you dosing anything for kh?