I see the advice on checking the hydrometer. Calibrate it and all of that jazz. The pain in the butt part is checking. Go through every stick, and even look at the boxes. Might be something in the fridge too. That would be easy. remove everything, wipe down with rubbing alcohol, air dry for five minutes, return everything. Check humi devices.
Now, in my opinion, probably just that one, but mold can spread, so it doesn't hurt to check.