Only issue with the Ultrasonic humidifiers is that they break/degrade over time with heavy use especially if not cleaned regularly with the special cleaning solution they make for humidifiers....which I found out is NOT plant friendly, the cleaner left a residue on the plants which stunted growth until it was 'wiped' off each and every leaf, pita.

I'd be very hesitant running any type of nutes through it as I'd suspect it would only foul-up the Ultrasonic device even quicker, as I have noticed they are sensitive. I'd save the humidifiers for vegging in dry climates/areas (<35%RH). .02