samr here, I have my zoas at multiple levels based on color and just testing what they like, my sunny D's are half way up my rockscape and are super bright orange, I also feed them roti mixed with reef chilli a cpl times a week.
My mowhawks seem to like a tiny bit less light, the fire an ice like a bit more, eagle and dragons eyes seem very happy on the sand bed so just give them a week or two and you can try moving them up a bit if you are starting them on the bed. feeding a little cant hurt either.