Help! Puppies Soiling Their Bed

[Kirty]

I have two foster pups here at the moment who have had a pretty crappy upbringing until now. I suspect they have been kept in very isolated, cramped conditions because they are very fearful and they also use their bed as a toilet. They are currently in quarantine so they are in a pen. I have put newspaper at one end and put their bed, food and water at the other end. They frequently wee in their bed though. They also wee right next to their water and food. They use the newspaper too, but I've never had such dirty puppies. I am hoping once they are out of quarantine I can teach them to use grass, but does anyone have any ideas to try to stop them doing this?