Been a long time since I've tried Rams, and I've had better luck with Bolivian Rams than with the others. What are your tank parameters? IIRC, Rams do better in higher water temperatures.

 

Temp is 80. Ammonia is always 0. Nitrite is always 0. Nitrates is usually at 10.

 

With rams, its sometimes more about what genetic material you buy (inbred specimens). The average ram in your LFS has been grown with use of hormones, antibiotics etc, in combination with no breeding plan to prevent inbreeding. The combination of these factors makes the fish incredibly sensitive to pretty much anything. beautiful fish nonetheless, but a pain to keep.
Bolivian rams in general have less inbreeding depressions. If provided correct water parameters, they are more likely to flourish than the ones you've been keeping. My father had a pair of bolivian rams for seven years in his south american community aquarium before the male developed problems with his air blatter.

 

If it makes you feel better, I've had similar experiences with GBRs. I just can't keep them for very long. I've been very successful with all sorts of fish, but not GBRs.