I'd take out/reduce the amount of PhosBan you're running on your system and see what happens.
Xenia does tend to like not so perfect water parameters, and your's sounds pretty close to perfect. Be very careful if you decide to dose iodine... its really easy to over dose.

A good rule of thumb as far as a reef tank goes
*If you're not testing for it, you really shouldn't dose it! *

Just my $0.02....HTH!