Sometimes, a virus makes it inside a camellia and it triggers this type of change. The yellowing of leaves gives me a hint that this may be happening. Other times, it is a variety whose DNA is not quite stable and develops these different bloom colors. I had one (which is yours?) that was supposed to be white with pink stripes and it started putting regular pink blooms from one branch and sometimes, the pink bloom has a few white stripes. Enjoy the show. If you do not like it, remove the the branch and see if that stops/prevents the mutation/sport. It may also be that it has gone back to the way that a parent used to bloom like.

Thank you! The flowers are consistent across the whole tree (as healthy and beautiful as this one) and the yellow bits on the leaves are not common at all.