Getting notifications with a delay on the iPhone

I get all the notifications on my iPhone with a delay. These notifications which get delayed are usually iCloud emails and iMessages. The delay is sometimes a couple of minutes and sometimes even more than 20 mins. I changed from iPhone 6 to 6 plus hoping that changing the iPhone would solve it but it didn't. The problem is on both, wifi and cellular data. I have multiple apple devices and all the devices get the notifications on time except the iPhone. i even tried removing iMessage account from the other devices but nothing seems to be working. HELP!!!