Reds in zoas turning brown in frag tank

[Danmuges]

Anyone had instances where zoas would lose their red colouration? My Emerald on fire and goblin on fire used to look very bright red now they just look dark brown.
These are in my frag tank which has been running for 3 months now. My other zoas seem on although not as bright as they should be.

 

[lapin]

Prob a light issue.

 

[TitansFan]

I second lighting. Mine always get duller and larger in size when further away from lights. Some zoas like stronger lighting than others.