I have 2 young ferrets, between 3 and 4 months old, that I'm having some serious litter training problems with. I had successfully litter trained both of them when I brought them home. After about a month of no accidents I gave them the run of an entire room, with several litterboxes. Less than a week later, they started to completely ignore the litterboxes and go whereever they please, I even found some in a drawer! So I put them back into their cage when they could be supervised. But they still will not use the litterboxes. I keep their boxes with nothing more than one piece in it to keep it marked. So cleanliness isn't the problem. I use Yesterdays News litter. Any suggestions would be much appreciated, if they do not stop doing this I will have to put them up for adoption, I live in an apartment so it isn't my house for them to tear up.