There is a growth spurt around 3 months. There is also a lot of reverse cycling that goes on when moms return to work. Babies love to use the night to make up for lost opportunities to cuddle and nurse! Teething tends to kick in around 3-4 months. You might not see those teeth for many months to come, but they are moving around in the gums. Kids also tend to get sick a lot when they start daycare- even the breastfed ones!- and that can cause increased night waking. Developmental milestones, like baby learning to roll or developing separation anxiety, can also cause more night waking.
If the episode of engorgement/plugs caused a big supply reduction and you would rather be a little more even, the way to get supply back on the left is to remove milk from that side more often and to drain it more completely. Sounds like that's what you're doing already, so keep at it!