Notifications not coming through on S3 mini

[Aina Oozageer]

recently the notifications (gmail, facebook, tumblr, snapchat) have not been coming through automatically, i have to go into the app and refresh before i get them. this problem started about a month or 2 ago, sync is turned on and i haven't changed any of the settings. Every so often (maybe every few weeks) ALL the notifications will suddenly come through like all the fb messages, snapchats even though i have already seen/opened them.