The discharge, if TOTAL discharge is bad because that's the coral basically giving up. After a TOTAL discharge the coral no longer has the ability to make food from light. Maybe times you'll see various discharges from our corals and sometimes it IS "adjusting" the amount of zooxanthellae for some reason and sometimes it's just part of it's normal process. I'd dare say there are many more discharges and other occurances that go on in our corals over a months time than most realize. The reason I say this is because I sit in front of my tank for 9+ hours a day here and work and then go home and stare at my home tank. This gives me time to see corals throughout the day and night and I would guess I get to see things that an occasional viewer might miss.
The colony looks VERY healthy.
Those yellow ones are simply Yellow Palys. Very common and add a LOT of character and movement to your tank. I have them here in my office and LOVE them.
