Our son is a bit older, 21 months, but what has helped him, (he's been doing the same thing), is putting him down a bit earlier for both the nap and BT.
I think it's just a bit of trial and error, trying a few new things, to see what will work for your LO. Some will respond better to a later nap, later BT, but some will do better if you pull it back a bit earlier.
At 21 months he's doing
WU 6:15-6:30
Nap 12:10-12:30 asleep (for an hour to 1.5 hrs, rarely 2)
BT 7-7:30 (asleep at this time)
We actually were putting him down later for both nap and BT and then I decided to go back to earlier times and it has helped!