@waylo.
Sad to see a Seasonic unit go, but after @8 years it's had a good run by any standards. Couple of things though. When it comes to voltages, you just can't trust software to be accurate. I don't know why this is, it's not a hard concept by any means considering the exacting voltages needed for cpu stability. By my Fluke multimeter, at last testing, my Seasonic m12ii 520w had a 12v output of 12.32v. According to speccy I had 10.7v, Asus suite was 11.7v, occt was 8.3v, hwinfo64 is 10.24v and bios is 12.30v. Seriously ppl, its nuts. So as to your 11.3v, I'm not entirely too convinced it was reported accurately.
In principle, a capacitor is basically like a spark plug, voltage goes in the anode, sparks across a gap and back out the cathode. Due to this, you get degradation as the molecules at the poles get dislodged. Capacitors do have a shelf life, the best Japanese caps being longer than the old chemical caps. Because if the degradation, capacitors loose ability, so your 330w unit after a year or 2 was closer to 300w, and after 8 years of life was probably closer to 240-250w in power output. It's not that it failed, it just got too old.
You should actually be happy with that age, more than a few units use such crappy caps they are usually only good till their 3 yr warranty runs out, if they last that long.
Anyways, nice choice on replacement psu.