What a shame you are a failed fosterer, at least these two are safe, but it would have been nice for the rescue to have had another pair of hands. Sadly fostering doesn't always mean you get nicely clean, healthy cats/kittens, although it does sound like the rescue should have done more. My first foster with fleas actually came through our vets, he was a pts drop off that they obviously never checked - I had taken in a stray the day before who had no fleas, yet he came from a house!!