I am having a major problem with fish dyeing. Let me start off with tank info. 150 gallon tank, 180 lbs of live rock, 3 inch sand and crush coral base, bio ball filter system, 2 Korallia 860 GPM power heads, Protein Skimmer, and heater. 2 clown fish, 1 fire fish, 1 yellow faced angel, 1 Whip Pink Fairy Wrasse, 1 Chimos, 1 Hipo, 2 cleaner Shrimp, 20 blue hermit and 10 snails, 1 Foxface Tang, Star Fish (cleaner), 1 unicorn Tang, 1 yellow eye tang, 1 Neon Dotty Back and 1 trumpet coral. The tank is about 9 months old and all has been going well until recently.

I added the Fox face and unicorn tang 2 months ago. The unicorn tang died in 3 weeks. Went back to the store and they gave me another unicorn tang and purchased a yellow eyed tang. The Neon Dotty back died a week ago. I did a 25% water change even though the water tested great. The yellow eyed died after the Dotty back. I noticed that the fox face had ich. The store sold me Ich Attach which is 100% organic and I did not have to remove the fish. Water still tests great. This morning, I fed the fish and the fox face still had ich but not as much. I gave another treatment of the Ich Attack. Tonight, the unicorn was swimming sideways and the fox face was being held against one of the power heads. I removed both fish and place in the quarantine tank. The fox face is covered with Ich. All the other fish seem to be OK; however the clown fish had been hiding in the rock lately. When I removed the 2 wish, the clowns came out and started swimming like they normally did. I did not notice any fighting in the tank. This is very frustrating. I am down to the shrimp, 2 clown fish, hipo, chimos, Wrasse and fire fish. It seems that newer fish have died and the original fish are doing fine, except for the dotty back which recently died. I clean the tank on a regular basis. I have been getting brown film on the glass which cleans off with little effort. I do not u se any cleaners on the glass at all and it is covered. The only new change was the Christmas tree which is about 4 feet from the tank. What am I doing wrong, this getting frustrating?