Any details on the tank? How big, how much rock (filtration) how much/what type of light, how much flow (what are your powerheads)?
And what about the params?? Need to know nitrates, temp, pH, sg, etc...
Personally i wouldnt worry too much due to the fact that its still opening up (even though its not all the way). It sounds like it may not have good enough flow or one of your params are out of wack..
Sidetracked, but its needs attention IMO...you say you've got a 50g tank. Is that fish list current? If so, both the tangs need to go. There's no tang that will do well in a 50g tank, ESPESIALLY a sailfin and/or clown tang...add the fact that you've got BOTH of them and that will be major trouble in the near future. Thats like 10 fish in a 50g tank...minus all the water displacement from the rock and sand and you could be lookin at about 40g of actual water.
If everything is tiny, they might be fine for a while...but once those tangs grow much that wont be good.