Fades out in dousing after 10min? or dimming out as if a dimming curve to no longer having useful output but still operating?
It in fading back in, restriking an arc or fading back in with constant light just more output after a rest in output?
So after cleaning and blowing out or replacing filters it's still dimming or dousing not clearly defined, than in a clean
fixture still dousing or dimming still. Your 412 lamp hours is good in defining it's probably not a lamp issue, but don't expect a Snowball well before 3,000 hours.
Operational fans means you put an ear to them of course in sounding normal to other fan noise.
Until further defined as dousing in lamp out/off or going noticeably lower in output - yes there is going to be lamp problems, but it might not be the lamp. The balance in testing this question is how many good lamps one burns
thru in solving the problem?
Serious
fixture warranty question if possible in sending it back for factory service. Even with questions above, I would say you did what you could short of wasting lamps in further testing.
Take photos of the lamp - it's core will be hard to take, and lamp pins. I note no failed lamps yet - though if having problems, best to solve before failed lamps.
Lamp hours in this class of lamsp is more a goal or imaginary concept for working but not useful output, but I don't see so far as part of the problem. This even if testing in a science lab. it's not with
pyro dust or
fog fluid or other issues this indicates environment of
fixture or
house different than expected.