Yes, it was likely the hiss that is present in the X32 as a baseline.
It bugged me a little bit when I first got the consoles, but then I connected an APB House Rack with outboard to the same speakers that were bothering me a little with the X32, and while the House Rack was quieter than the X32 by a bit with the HR master down, it was vastly louder when set to unity, whereas the X32 was the exact same hiss level at infinity and unity.
The House Rack has always been perceptibly quiet, so I've never at all worried about the X32 hiss level since that comparison.
Again, as I said before, last night it was a little noticeable when the amp was at no attenuation, and perceptually gone when at 12:00. If you weren't listening hard in a dead quiet space, it would have been perceptually gone at full. And it turned out the band literally barely used the monitors anyway (big jazz band).
Edit: These are the non-DSP amps.