Hi all and Happy Holidays.

I have a 29 gallon mini reef (live rock with corals,) cleaner crew,
yellow tang, and 2 chromies. Hang on PS, 20K coral life MH.

About 6 months ago I noticed that my mushrooms were not as opened as
they used to be, and my button coral was not extending its polyps fully.

I realized that the bulb was well over a year old and I promptly
replaced it. However, since then, the coral and shrooms are still the same.

Fish are thriving and growing (too quickly,) and water parameters are
all WNL.

Could it be that the ballast is old (4 years,) or did my corals suffer
some irreversible damage?

This has happened before but the corals returned to their normal selves
several days after I installed a new bulb.

Your help is very much appreciated.

TIA,

Rich