Dog Started Pooing Inside?

I have two dogs, a GSD and an Akita which are the best of friends. The GSD is 8 years old the Akita is 2 years. I had her from a baby. Last month she has taken to pooing inside. It can happen anytime and they are not small packs.

I take her out with the GSD. The Akita will do a little bit outside then come back in and when my back is turned to her, she will start to go. She does this in the kitchen and lounge. All the floors are tiles which helps a lot, but this can't go on.

By RP