Welcome!
Are you crate training your two? Most likely they are putting markers in your house to let other dogs know they live there. You need to (1) clean every stain with an enzyme cleaner like Nature's Miracle; and (2) either restrict their movement or watch them more closely (probably both).
Yorkies can be very challenging to house train, so I suggest reading up on crate training. You can also use an xpen. You are all in for an adventure.
