u/Puzzleheaded-Put4109

My Chinese (red with yellow center) Camellia is dying, I've had to cut off one of the stem/trunks already, not entirely sure what's causing it, I've attached photos, but otherwise I've seen some ants on and around it, some aphids that have been quickly dispatched, the trunk that Ive cut off died within a couple weeks, slowly getting browner and the leaves getting dryer and dryer, the 2 trunks left aren't getting dry leaves yet but some have black spots and are going brown and the buds aren't budding.

The plant gets sunlight for around half of the day, and I water it every couple days, no specific soil just generic soil if that's a thing, I live in south east england

Thanks in advance for any help