That can be a common play behavior amongst puppies, so I think it is pretty natural. I think the advice already given here is probably good

As a side note, my two who are altered, occasionally play the "humping" game still with each other . And yes, Tasha takes her turn too! Even though she is a female. But between them it seems strictly play and not dominance behavior at all, because Tasha is clearly the alpha between the two and yet this just seems to simply be a game between them off and on.