swollen chest area

Morning, abit worried about Ruby yesterday morning fine then suddenly she started to go down hill, her whole chest area ballooned up, not just her crop, and she was drinking lots, so I thought kidneys as she is now 3 and a rescue hen (we lost Hetty a month ago) she made it through the night and ate her porridge and is wandering around, she is still swollen but not as bad, I don't think her breath smells, is this as bad as I think?my Dad is on standby just in case.

Thanks joyfull, i didn't think it was any of those because the swelling was severe over all the chest, thankfully swelling gone down alot and I can feel she is crop bound so been giving her olive oil and massaging her crop (which she loves!), she is better in her self,  is there any thing else I should do to help her?