Do you think so? I dunno ... I know nothing about the caramel morph aside from what I've read on the forums, but I think it is totally feasible that caramel females may have naturally lower fertility than other morphs. It could be that for whatever reason, their genetics dictates that they produce fewer ova per ovulation than the average female BP, the conformation of their oviduct may be somewhat off, or perhaps have a slightly less hospitable environment for sperm (too basic or too acid, or what have you) ... Who knows! (I sure don't -- it'll be a long dang time before I can afford a caramel female to prove it for myself)
If it does turn out to be the case that caramel females have low fertility, I don't think it'd be the end of the morph by a long shot -- it would just be another one of those morph "quirks" that breeders need to bear in mind, like not breeding albino to albino in boa morphs.