I have one very poorly pup...but the other four

well....
They are kept in the conservatory, which is heated for comfort...all furniture removed, and it has a tiled floor.
We have to clean the floor daily at least three times... (naturally) but we are having to change the bedding twice a day too...each time I put nice clean bedding in their big bed they pee on it

am I doing something wrong?
We have the puppy pads...but sure as anything, soon as the new blankets and quilt go in...they pee!
Are they just marking it? Should I leave something in thats smells like them?
At a loss as to what to do...HELP!
Breda