Newer iPhone notification delay compared to older iPhone

so i recently bought a new iphone and i have an older iphone which i dont use. however i noticed the older one gets notifications faster than the newer one and theres a noticeable 5-8 second delay.

for example, i have an authenticator service installed on both phones for some account i want to log into. when i try to log into something using that authenticator it should send notification to phone (which you then have to confirm you are logging in). the older phone gets notification first than the newer one which gets it later and i dont want this.

another example of it happening is when both phones are logged into the same facebook messenger account and someone texts me there and the older phone getting the notification faster than the newer one.

how can i make it so they get notification same time or newer one gets it first? thank you.