That is a really good point regarding kidneys.
She didn't show any real signs of an URI near the end, minus the mucus during the shower. No popping or squeaking, no deep inhales.
I got up for work and put the dragons back in the enclosure (I take them to bed with me...) and checked on her as I passed by and could not find her. I put the dragons away and ran over to check, stuck my head in, couldn't find her, and then I saw a dark shadow through her food cup

and it was her. She passed away and fell into her cup.
Last night she did appear to have some swelling on her lower left side right before lights out that concerned me, but when I removed her to look her over, it seemed to go away, so I figured maybe she was just turned funny when I saw her but was still concerned. I'm wondering now if that was the start of her system failure