I have been looking for a long time at euphillya because they are a great coral that I was always lead to believe were extremely easy to take care of, when I took care of them at the store they always did super well so I didn't think about it.
That being said: it seems they are more complicated than I thought. My tank grew anything I put in it. I got a tiny torch and it opened and the skin started overtaking the base skeleton again slowly and then when from 1 head to 3 heads. I got a hammer the had skin all the way down to the base with baby branches everywhere, as soon as it got into my tank it started to recede but it was opening nice and full, then the skin stopped receding and started crawling down the skeleton slowly over weeks. My tank was half coral and half macro algae and parameters were perfect. I wanted more space so I plumbed in a sump and moved my macro algae down to the sump with a cheap light on it. Tank went 2 weeks doing well, then crashed and smelled like rotten eggs, dinos absolutely everywhere, it was savage. So not only had I messed up my nutrient export but I created a huge amount of anaerobic bacteria creating a bacterial imbalance. My torch lost months of growth, my hammer lost all the flesh on its skeleton, everything was sad, only acro, toast. I moved to a larger tank and have moved the macro algae back into the tank under a better light. Tank went through diatoms that cleared up and we are doing a 10% water change every other day to keep things stable so we don't lose all of our coral we worked so hard to grow and acquire. We have another bunch of macro algae starting to grow and I added to it 2 weeks ago the tank is starting to come back. Current parameters are still great. But I say all this to say I think there is something we are missing, tank maturity I think has more components than just good parameters.
I would say your tank is cycled and the parameters are good but there is something more to it and I'm trying to figure out what that is. I hope you won't lose your corals but I would say the skin has probably started to recede. I would start dosing amino acids and feed the the tank heavier, your water may be sterile and carry little beneficial nutrients for your coral to absorb from the water column.
Sorry for the book but this stuff is pretty important to me and I find it very interesting.