Torch coral randomly stoped opening need help!!

hi everyone 2 of my torch coral were fully opened and look happy as can be but for the past three days things have changed

I tried moving spots to see if that would work,and nothing

Ph8.0
Ammonia 0
Nitrite 0
Nitrate 20
Salinity 1.025
Calcium 500
Dkh 12.4




Any insight would be much appreciated

 

Hi, I have a Duncan and had it over a year doing well and was growing extra heads then one day it started to close and recede it did this for 8 months, I kept moving it around the aquarium now and again to see if it would improve. It is now after 8 months that it has been constantly opening. The only thing is that my nitrates have been up to 40ppm, plus When I was feeding my other corals, with a turkey blaster I made sure I squirted around the Duncan coral even though I saw no reaction. All I can say is persevere they must be hardy as it’s taken 8 months for mine to come back, I thought it would surely be dead by now. Hope this has helped.

 

Here is a photo of the Duncan before in its glory,, then when it retracted for 8months, and now it’s come back.