Coral Disease

1st of all hello this is my 1st post I have been here awile though. My tank is a 39 gallon with a 20 gallon fuge/2nd tank on side of main. The main tank has been setup for about a year and a half.
When I bought this zoa colony it had green and brown zoa's all over it not too long after the green zoa's died off and the brown ones took over and started growing onto the LR that the frag was sitting on. They were doing good for a few months then they started to look like this.





They have been like this for about 5 months I have no idea what is wrong with them but none have died.
Water parameters are ok but had fairly high nitrates until recently ~20ppm

 

they look like palythoas mine do it some also what lights do you have?

 

I have dual 96 watt PC's a 10K and actnic. The main colony used to be at the top of the tank but I moved it lower to see if it was getting too much light but it didnt help.

 

Keep a close eye on and make sure you don't have any sundial snails lurking about in vicinity...

See: Zoa eating Snails

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do you have one 10k/actinic or one of each a 10k and an actinic. big difference its either 96 watts or 192 watts. what are your iodine levels?

 

I have 2 96watt 192 total 1 10k and 1 actinic.
Iodine levels not sure havent dosed iodine for about a year though.

 

depending on how far they are away from the light matters. you should get enough iodine with water changes. to much isnt good either. do you have a test kit?

 

The addition of iodine and intense lighting are essential and ideal and will go along way to ensure your soft corals are thriving.

 

I have test kits for just about everything except iodine. I do have a bottle of Kent iodine supplement but I dont want to add if I cant check. Will probably invest in a test kit if you guys think its important for softies seeing thats the type of corals I have in my tank. Think I could add a little to see if it helps? Will it hurt anything?

 

I did look in with a flashlight to check if anything was eating them didnt see anything. They do close up at night like normal they just dont open up like they used to and they look nothing like they did when I got them but they are not dying either cant figure it out.