Satsuma?

With where you are located it's possible that the brown on your leaf tips is a result of salt build up in the soil as you've cut back on watering with the cooler weather. Because you have a small tree if you're watering by a dripper or small amount in general the naturally occuring soil akalinity will take it's toll on the roots. Try giving a deep watering to get the salts below the soil line - no new leaves will be produced until the spring, but you'll get built up minerals rinsed below where the roots are growing. Don't fertilize until spring.

Crista