I've noticed that my zoas tend to lose color and be more translucent when my lighting is too high, or my water is too clean. Try moving them to a lower spot in your tank and increase you nutrients if they are super low.
Hi mate, just thought i'd chime in i grossly underestimated the power of my AI prime HD in a Nuvo 10 Gallon. ive brought my lighing intensity from around 90% to 35% and my zoas have started to regain all of their colour in only two days.
my nitrates are sitting at around .18 which isn't super clean but not super dirty