Saw a very nice and big clarion angel, some rock beauty angels and french (I think) angels, and quite a number of flame angels, yellow-eyed kole tangs and yellow tangs at LCK201 yesterday.
Tried hyposalinity treatment? May be some hidden (invertebrate) parasitic organisms and a hyposalinity may kill those parasites... How about using Chemipure to help treat the water?
What sort of media do you have in your sump to accommodate anaerobic bacteria which breaks down nitrates? Meanwhile, suggest you use this product called Chemipure to clean up your water.
Hyposalinity treatment for fishes => reduce specific gravity to 1.008 and hold it there (for up to 3 months, I think). Works for me. You can read online to confirm.