Two corals are looking bad

#1
I think I posted this original post in the wrong section sorry. I have copied it and pasted to general. I have a fairly new Red sea reefer 350. I perform 20 percent water changes twice per month. I run an aqua medic acone 1.0 EVO skimmer. RODO water with 0TDS out. My parameters are nitrite 0. temp 78, calcium 435 ppm. alk, 7.7dkh, ph 8.26, phosphate 0, mg 1440, nitrate is at 6ppm, and salinity is at 1.025. Water change this weekend. I have a sandbed that's about 6 inches deep with about 100 lbs of live rock. Lighting is two Kessel's 350w at about 9 inches off the surface. Lighting is run 9 hours a day. The tank is about 75 gal show and 25 gal sump. Live stock consists of 1 purple tang, 3 firefins, Tomini Tang, two cardinals, sand sifting gobey, 1 one spot foxface. 5 turbo snails, 5 hermit crabs, 2 cleaner shrimps, 2 emeral crabs, 5 cereth snails

I lost 1 clown fish a week ago and then another a few days ago. I could not find them and have a net cover on the tank from BRS, so they did not jump out, they were healthy before the loss. I think my long tenticle plat coral eat them both but not sure. The reason I say this is the followig day after losing the clowns the plate coral was all puffed up like i had never seen. Now to the questions, yesterday I feed the tank and noticed that the long tenticle plate coral is showing some skelaton on one edge and my maze coral has a few very dark spots almost black the size of about an 1/8 inch. I have done some research on the long tenticle plate coral and now think it is starving so I am going to hand feed it and cover it with a cut two litter bottle to keep the cleaner shrimp from stealing the food. Do you think the maze and plate coral issues are related as I am at a loss for what is going on with the maze coral. On a side not I have a few other corals that are doing fine. Thanks in advance for any assistance.
 
#3
I will post a few in the am, after making some RODI water and looking over the tank it appears that some of my zoas are melting. Wow things can turn south fast, I am at a loss. Making a water change in the am to see if that helps.
 
#6
0 nitrate and 0 phosphate is too clean for corals specially LPS. Your plate could be receding due to a lack of nutrient in the water column. I would shoot for .03 phosphate and 3-5 ppm nitrate. Maybe don't do so much water cahnges.
 
#7
Here are pictures of the two corals. The maze coral has dark brown spots that it never had before. The long tentacle plate coral has just recently been receding and it has not been extending its tentacles. Both corals have been looking very good up until a couple of days ago. Any suggestions?
 
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