Sorry to here about your GBR dying. I have kept and successfully bred GBR's for the last few years. Even with my experience, I occasionally get new stock which act very much like your GBR. The absence of non-vibrant coloring indicates stress, and in my experience some GBR's die from being too stressed. While I try to keep my nitrates lower than <10 in my GBR tanks, I do not think that would be the cause of your little Ram's stress. Sometimes they just seem to do this. Keep trying, these little fish have awesome personalities when you get some good ones.
How long were they in your
LFS?
With Cardinals and Rams, I like them to live at least a week in my LFS tank before I take them home. My LFS (a really good one), will let me know if the batches have been hardy, and on more than a few occasions have told me not to buy the ones they have.
What was the temp in the tank? (I may have missed that)
Last, was the fish eating and what type of food?