some fish are splashers like ..... splash tetras. Some of my fish splash when i feed them like my severums and larger rainbows.
I do have multiple water spots on my reflector, no rust.
You need to train those splashers to be more "housebroken".
None of my fish splash water, so I only get water droplets if bubbles break at the surface.
That reminds me: I spent some time looking at one of jazzlvr123's tanks recently, which had MH pendant lights over it, and CO2 injection was primarily by ceramic disc type diffusers. The light showed up the cloud of tiny water droplets that hovered above the water, from the bursting CO2 bubbles, tiny as they were. That was when I discovered just how hazardous it could be to have bare electrical stuff close to the water. With that type of setup I would expect to see water spots on a fixture reflector if it were only a few inches above the water.