[bWY39]

Some years ago I experienced a similar situation with my Cocker Spaniels.

I had an adult dog and when I introduced a puppy my adult dog started toileting in the house.

A behaviourist told me it was "attention seeking" because of the new puppy and suggested I give the adult more attention than I offer the puppy.

Well I met it half way and gave them both the same attention making sure that if I fussed them I fussed the adult first. If I gave a treat then adult fist and so on.

For me it worked but each case is different so perhaps you could try it out and hope.