So Bella pulled a surprise molt on me last night.
I used to always get warning, back when her tank was upstairs on the main floor, because my toddler's running around would stress her out enough that she always developed a bald patch on her abdomen. When a molt was imminent, it would turn black, the new hairs underneath becoming visible through the old skin.
But the stress was exactly why I moved her tank down to my office in the basement, where the boy doesn't run around. It worked; she seems much happier and less troubled down there. The downside (which is really an upside) is that she doesn't get that bald patch anymore. So I didn't see the molt coming. I just happened to look in on her last night, and there she was, sitting next to an old skin, and looking tired.
There was a white, ugly-looking stump where one of her legs should have been. I don't know how it happened, but she lost one in the process somehow. Severed right at the cephalothorax. It'll grow back in time, but she's stuck with seven for now.
Fortunately the wound had clotted, and wasn't bleeding anymore. Bleeding can kill a tarantula; they don't have muscles like we do, but instead move their bodies almost hydraulically, using changes in blood pressure to articulate their limbs. Which means if a spider loses too much blood, or becomes otherwise dehydrated, they may not even be able to crawl to the water they desperately need.
But I think she'll pull through. She's tough. Here's hoping.