Hi, just dropping in

From memory has your LO always been on the lowish side for sleep needs? I agree with Naomi you could be hitting the beginnings of the 1-0, though if canines are coming it's very hard to sort out exactly what's what. Could molars be on the move too? We had a hideous sleep time when they arrived, long NWs (for which meds did nothing at all) or real trouble settling at BT. We also had a period of time around 2yo when we got NWs every night for weeks on end and I couldn't find a good reason at all....not much help but might be some comfort to know that sleep can go wonky for reasons out of our control.
If it's not teeth/development causing the disruption, I wonder whether you might need to consider pushing nap later to 1.30 and capping to 1h30 in the first instance. I know that leaves a short A to BT but a similar routine worked well for us at this age (though we also started getting the odd nap refusal around now too). From what you've posted I'd think it unlikely it was the A time to BT that was causing your issues......but I don't know for sure.
Did you have a peek at the 1-0 thread? What did you think?