I think it is time you discussed this situation with whoever is in charge of your lab. It will only get worse and worse otherwise.
I don't understand why this sort of malicious ganging politics was allowed (even seemingly fostered) at the university where you did your master's.
But remaining silent about it is only going to make these sort of antics the norm around you.
So get a dependable witness and tell the situation to the senior academic there.
It may be that in the end you would be better and happier in another more positive (as a result of more vigilant professors) department.