I just recently planted this lovely R. citriniflorum in a pot. Now the leaves are brown and dying. It is a mail order plant from a reputable nursery. I put it in a 11"X9" ceramic pot with Whitney Farms Premium Planting Soil. It is in the shade with ample light. I have no idea what the cause and/or result will be. I'm hoping someone will have an answer. The nursery has been notified and will no doubt respond too, but DG has a much wider knowledge base.
Well, a couple things I can think of (in no particular order) The pot it's in looks too big for the plant, this can increase the probability of overwatering, which could eventually lead to leaves turning brown and dying. Another possibility is that although it sounds like it has some shade, maybe it's getting more light than it was getting at the nursery (plus there was the time it was sitting in a dark box). If it's getting more light than it was used to, then it may have needed to be adjusted gradually to the higher amount of light. I've also had this happen to lots of plants that I buy from nurseries in climates that are more humid than mine--I have to wean them off the humidity gradually by misting them frequently for the first few weeks I have them or else they wind up looking exactly like that. Many have come back later and grown new leaves eventually, but some haven't.
Hopefully if this was a good nursery that you got it from and the plant started to decline right after you got it then they'll replace it for you too (even if they do, I'd keep trying to nurse this on along and see if it comes back)