Mold / mildew in incubator?

[HeritageFan]

We have been running staggered hatches (2-3 weeks apart generally) most of the summer.

We have 2 HovaBator forced air incubators. One w auto turners, a 1588, and 2370 as a Hatcher. Both w humidikits.

The Hatcher gets shut off, cleaned, has time to dry out- and gets set up again 2-3 days before lockdown to make sure that the conditions are the same when we swap bators.

But the 1588 has been running pretty constantly.
I noticed some mildew growing on and around the fan... so I ran my last batch, pulled everything apart, and cleaned everything as well as I could.

Then I got another duckling order, so I got it up and running again, and the mold came right back.

Has anyone else had an issue like this?
Is there a way to clean it better than disassembling the forced air unit, cleaning w warm water/ paper towels/ brushes (I don’t want to make the plastic fan blades brittle w vinegar or a more harsh cleaner)... setting in the sun for a bit?
The photo just shows the housing, but the fan blades also have the white mildew / mold.

I can’t believe I’m the first one to deal w this, but I didn’t see anything on the forums about this issue-

It usually runs at 35-40% humidity, depending on what we are hatching.

 

[nuthatched]

Is it possibly hard water build up?⁷

 

[HeritageFan]

There is a chance that could be the case- as we are on a well and I used our water- and not distilled water. The well water here tastes fantastic, and we don’t have a lot of mineral buildup in our sinks/ tubs/ toilets.
But
In my experience, mineral buildup is “hard”, and this seemed more like mildew.

I guess maybe I should pull everything apart, clean, set out in the sun, and try to only use distilled water next spring?