Anastasiya Komarova

Hi there, I have a first job paying £39,140 gross annually, and this is my main job. However, I also have a second job that pays me £360 a week gross (£18,720 gross annually). I make around £57,860 gross annually. My tax code for last year on my main job was 823L, but it has now gone down to 277L. The tax code for my second job has always been BR. Why has my main job tax code changed so significantly, and what should my tax codes actually be? Many thanks