Oh Jen, it makes me so sad to read this, because I always admired your little happy and healthy cat herd...but maybe with one cat starting the spraying some of the others might follow and the addition of the fosters supports their confusion...

I am so sorry, but as an owner of only one cat I can't give you a proper advice here...I just wanted to let you know that I hope it will all work out and that you'll be able to continue fostering cats in need...