If it helps I was in a very similar position just before Christmas. I've already mentioned my rabbits, but to recap:
Thursday - saw mother limping, thought nothing of it, assumed she'd landed badly from jumping off something and got a sprain
Sunday - "Kit" (over a year old by now) 1 is limping - take her inside and realise she's paralysed at her rear legs. Take all of them to emergency vet. Kit 1 kept in, vet not worried about mum, take others home.
Monday - Kit1 dies.
Saturday - Take remaining 4 rabbits to vet for vaccinations. Mention mum's limp. Vet reckons she's fine, but, she's lost an awful lot of weight. If I'm concerned the following week he can do bloods and x-ray.
Tuesday - Mum goes in for the above. She's lost more weight in the meantime (about 15% of what she was on the Sat, means she's lost nearly 50% overall), barely eating and totally lifeless. Vet sends home 3 days' worth of medicine, but warns me that if there's no improvement she'll have to be pts.
Now, the problem was that I was going to my mother's for Christmas on the Friday and had to leave early, meaning that, if the worst happened, it would have to be DP who took her up to do the deed. So, when I came off the phone from the vet I said that if there wasn't any improvement by the Thursday I'd book an appt for that day and have her put down then. It wasn't giving the steroids their full time to work, but I thought it would be the best solution all round.
DP was not happy (despite him not having much to do with the rabbits) and refused to let me do that, saying he'd deal with it on the Friday if necessary, but I was awful to be thinking like that. As it was, the steroids kicked in straight away, and she was back to munching fairly enthusiastically that evening. Another one of the kits went the same way, but, luckily, the vet sent more steroids home for both without another consult, and DP was on rabbit duty for the next week. Both are back to normal, mother has nearly regained all the weight she lost (but, to be honest, doesn't need to put on the rest) and they're back outside with the other two.
Still no idea what caused it.
So you see, you're not the only one. I don't feel guilty in my case, but DP is still horrified I was planning to put her down.