what is bothering my Zoas?

all corals in my tank are doing great except 2 zoa frags. these frags are the first that i introduced in my tank. they were doing great. always open and expanding. i have 2 other zoas that are doing good. (well 1 of these 2 i saw today that the pollyps are thinner than usual)
what i noticed is that the pollyps are shrinking in size and 1 of the frags lost some polyps. and this 1 is now always closed. i see 1 of its polyps open a bit. there are no evident parasites around them.
my tank is 75g param are in check (only nitrate goes up to 10 max)
tank inhabitants:
fishes: yellow tang, maroon clown, damsels
corals: Mushrooms, candycane, hammer, frogspawn
cuc: cleaner shrimp, peppermint shrimp, snails(turbo, nassarius, astrea) and hermits.
lights: 4 bulb T5ho fixture
my theory around the issue is the peppermint shrimp is the cause. i never caught him redhanded but since he was done from the aptaisias these zoas started shrinking.

 

how far from the light are they?

 

well they are on different levels. the light is about 6" above water lvl and the frags are 6" to 12" form water surface.

 

hmmm....I had the same problem that your having. Mine were lower in the tank. I moved them close to the light and mine seem take off over night. Huge colony now.

 

Did you look at night for Sundial Snails? It has to be at night hours after the lights go out. They drain the fluids from the zoanthids.

Melevsreef.com - Sundial Snail

Next I would consider dipping them in CoralRX or eqiv.

 

I never noticed these guys but i donno if the tiny baby snails i found yesterday are from the same family of these (but i saw them out in the day).
i will look tonight, do you know how big they are?

 

The link for ReefCentral that is attached to the link I posted gives a good reference for size. I would say about the size of Pyramid snails or a little larger.

 

i filmed my tank during the night the only creatures that i saw were tiny shrimp-like creatures (assuming these are pods) and some bristle worms (that came no where near the frags)
my laptop crashed and today i got it back from the geeksquad i'll upload the movie i took as soon as i restore the files tonight.
i moved the rocks with frags closer to the light and i'll see how this will affect them.
btw, my bulbs are 3 actinic and 1 purple, is that combination good? should i change 1 actinic to 18k or other kind of bulbs?