All three of mine had jaundice, dd1 was a premmie my waters broke at 34 weeks, she was under the lights for 2 days, it took her a few months to fully recover, she was fed every four hours as she was sleepy for quite a while.

Dd2 was born at 37 weeks, and was borderline but didn't go under the lights. She was much more alert and fed on demand.

Ds was 39+4 and had to go under the lights for 2 days as well. He was much quicker to recover than the girls.

With Ds I was tested for blood incompatibility as he had a low grade fever but it came back clear.