ncolon, how long have you had your clams??? What lighting did the clams come from, if you know?? I have gotten clams over the internet and had pics sent of what they look like prior to shipping and after acclimating them to my tank, they look completely different. The different Kelvin rating of your lights will play into the color you see the clams to be, even from above.
Just for example, I had wanted a green patterned
maxima clam and ordered a beautiful one, under my 65k iwasaki's the clam is blue where it was green under 10K's.
If all else like water params, are good then I would not worry about the clams health. If it is extending it's mantle then it is a happy clam. The lighting may be the whole deal here.
