Thanks for the advice all.
Fluid is well within its' 2 year life, having only been replaced in July of last year according to my records. This was when I replaced rear discs and pads. Fronts were done (also by me so the below is no doubt my error) in May 2022.
I did have the brake apart and inspect yesterday. I think the inner pad itself may not have been fully clipped into the piston, one of the three 'prongs' I think was not seated properly, and it tried to pop back out again as I replaced the pad. I think this may have been causing it to contact the disc when running and wear unevenly, but only on the small section where the pad was 'sticking out.'
Anyway, there is plenty of meat left on pad and disc, all are now clipped in properly, cleaned and regreased so I'll keep an eye on it from here.
See photos:
https://ibb.co/4YcpyY1
https://ibb.co/YNJCgVK