I have a couple of clams and I had read somewhere that if the mantle looses its color as in gets white edges or white pigmentless stripes that the clam was not getting enough light is this the case or is there any other reasons for this? sps seem to be doing fine I have seen this in other clams in other peoples tanks and they seem fine just a little concerned about mine they are under a brand new 250 20 k xm and have had no previous symptoms of this any Ideas