I am so VERY sorry to hear about Butterscotch! But please take the time to retest the other 2 as Leukimia is the MORE infectious of the 2 diseases. I do not like to correct people, but it is FIV that is spread through deep bites, FeLV can be spread as easily as through a common water dish. If the other 2 test positive at least you will know and can prevent others from becoming infected.
I wish only the best for you and Butterscotch.
{{{{{HUGS}}}}}}}