My zebra finches keep peeking each others beeks!?

Today I gave them some apple and they loved it. One of them ate some of the apple then the other one was peeking his beek! What are they doing?|||Birds that are friendly with each other will regurgitate to one another, meaning they will actually feed it's friend partially digested food into the other ones beak. This is normal and they are just showing that they are friends.|||they could be playing w/each other or finding ut there pecking order again|||They are either playing with each other or cleaning each other