i think my 3 year old lab is becoming park-aggressive and i need outside eyes because i cannot tell if its him or if the mix of dogs at our park genuinely changed

Murph has been going to the same neighborhood park since he was 4 months old. Hes 3.5 now and we go almost every morning at 7am, weekday mornings only, never weekends, never afternoons. Same crew of like 6-8 regular dogs for almost three years. He was always the chill one. The dog you point to when youre teaching a puppy how to read body language. Never started anything, never escalated, perfect park dog.

About two months ago a couple new families started coming to our park and the mix shifted. Two of the new dogs are intact young males, one is a high drive shepherd mix that gets locked in on chasing, and theres a dog reactive husky whose owner just lets her off leash anyway. The vibe is different. And Murph has started doing things he has never done. Last week he put a young goldendoodle on the ground and stood over him with stiff body for maybe 4 seconds before the owners pulled them apart. No bite, no contact really, but i have never seen him do that. Yesterday he did the same thing to a small terrier and i had to physically step between them.

Here is where im twisted up. The other regulars who have known Murph for years are telling me hes not the problem, the new dogs are stressing the whole park, and im seeing a normal dog respond to a chaotic environment. But i can also tell when im rationalizing because hes mine and i love him. He has never done this in 3 years and now hes done it twice in two weeks. Both times the smaller dog was being kind of rude and getting in his face first, but thats also a thing well trained dogs are supposed to handle without putting another dog on the ground.

How do i tell the difference between "my dog has hit a developmental shift and this environment is no longer safe for him" vs "my dog is being a totally normal dog in an environment that has gotten worse." I do not want to be the guy in denial about his own dog and i also do not want to take this away from him if hes actually fine. Help.