I think I killed it!
About a week and a half to two weeks ago, I started up a starter using the fruit juice method (I used apple juice with a touch of added ascorbic acid, based on reading all the reasoning behind the method). It didn't do anything for the first 4 or so days, then it slowly started to bubble a little bit more with each feeding (at which point I put it on water and rye flour, instead of my acidic juice and rye flour mix), until I finally, after a week and a bit, had what seemed to be a good, tasty starter. It smelled yummy. It rose well. I made sourdough pretzels with it and they were TO DIE FOR.
Well, I was running low on rye flour but wanted to keep it going without refridgeration for another week or so to let it develop a bit more of the "sour" flavour. So I fed it unbleached white yesterday. It gave a half-hearted little bit of bubbling. Even after carefully weighing the white flour and adding more than I should have needed, it went really watery. Overnight, it seems to have developed a strange odour that reminds me of the ketone experiments I used to do in chemistry and biology class. It's not rancidly nasty, but it's not the nice smell it had previously.
Today, trying to salvage it, I added rye flour again. So far, there hasn't been a SINGLE bubble Did I kill my starter?