To be honest, they do look a bit skinny (slightly concave stomach). Problem is, he accepted the state of the fish when we went through with the transaction at your doorstep.
I would have personally backed out of the trade once I saw the fish in person ONLY because I've had a pretty bad experience with some electric blue rams which i got from the LFS wasting away slowly (I learned my lesson). I managed to save 1 of the three i bought but the other 2 were not responding to any of the treatments i tried (prazi, metro, garlic, etc)...but again I didn't not blame the LFS, i was more disappointed with the supplier. I have since bought 2 more rams from the latest stock that came through because they looked amazing! A marked improvement from the previous batches and i took my chances with them. I even got a pair which have already spawned...and are putting on weight rather than losing it.
But anyways, as you stated...within 2 weeks there are too many variables that could explain their death. You had them for a long time with no problems, while they deteriorated rapidly in his care.