Is moving after bowing and returning to it again considered an increase in bowing, and what is the ruling on the prayer in this case?

What you did, a slight raising during the bowing (rukūʿ), is considered a minor movement, which does not necessitate a prostration of forgetfulness (sujūd al-sahw). Therefore, your prayer and the prayer of those behind you are valid. It is advised to disregard whispers (waswās) and not pay attention to them.