I came home today and noticed that 2 of my chromis were hiding. Ive got 4 chromis, a tang, other misc items and a few corals and poylps. Everything else looks fine. When I look at the 2 chromis, they look fine but are hanging out really close to the rocks in tight places with their bodies pointed upward. They came out to eat but went back. Are they sick or could they be doing something else weird?