It could be a growth spurt, but you say he doesn't seem hungry, he may be just hungry enough to wake up, but not to need a big feed, so can be settled back. Does he have any feeds between 7pm & the wakeups, if he doesn't then think it could well be hunger, he may have made it through before, but age & probably more active, he definitely has a right to being feed... an 8-9hour stretch is really good at this age.
The other thing I have noticed with my 4.5mo is that he is waking earlier, so I plan to increase his awake time & activities ever so slightly, as I don't think he is quite tired enough to make him sleepy enough to sleep the last few hours properly.