When Pouncette had Gary and Ivon at the Found Cat Hotel , I also found the tiny head of a new born Kitten , Pouncier who she had eaten , all that was left was the tiny head.
That Kitten was either still born or mal formed and was eaten so Pouncette could comcentarte on her Healthy Ones.
You shoulnt blame yourself, you did all that you could and it could be that BW and Spike had something wrong that you couldnt sense, but Tootie could.
Or had a fit of anger and killed them, and now feels sorry.
You did the best that you could and BW and Spike as Eternal Kitten Angels will be there to greet you in Paradise.
One Fine Day.