23/11/2021
Any suggestions / advice welcome ...
At home we have two blue staffy puppies (girl who’s 7 months & boy who’s 5 months).
They are both very well socialised dogs, with daily walks to our close dog park as well as nearby commons etc where others dogs walk.
In the past 2/3 weeks our boy puppy has started to show aggression to other puppies (same size and smaller than him).
Most recently today, we meet our friend with their puppy xl bully and again he turned & got his hair all up, straight tail & got his teeth out to bite.
In the moment of course we are frustrated with him, and his new recently behaviour so sturnly tell him off with an also straight on the lead.
We have thought of the possible reasons as to why -
He has had “bad ears” with continuous ear infections, and was thinking maybe the other puppies are going for his ears making him turn?
He is showing dominance in front of our girl puppy?
Or he is reaching an age where his levels of testosterone hormones are starting to peak? 
Today, after the 4th time he has done this, we have had to buy a muzzle in the case that he does cause harm to another persons dog and for his safety also.
We would be grateful for any advice / suggestions that would help us in this matter, as although he is the most soppiest and loving dog at home with us and my two year daughter is that the aggression towards puppies may defer to us also and more importantly my daughter.
Thanks in Auckland new Zealand