transition from 3 to 2 naps

Danielle
What age did your LO go down from three to two naps a day? How did you know it was time? My LO is suddenly having a hard time falling asleep for her naps but I can't tell if it's teething or that she's not tired? She's giving cues that's she is sleepy but having a really hard time falling asleep. 
Thanks in advance!