All units received new tile, new cabinets, appliances, tub surrounds, fixtures etc.

We upgraded the kitchen, renewed the floors, added stainless steel appliances, then made the attic a finished bedroom.

The only mold you have to worry about is if the unit was leaking outside the appliance, which does not appear to be the case.

I have been primarily doing buy and hold in the local area since 2004...and all I have to show for it is a masterful appliance repair skill set

Do some cosmetic upgrades (paint, countertops, cabinet hardware, appliances, flooring - if allowed - see governing documents, lighting, etc.) to attract quality tenants, command market or above market rents, gain appreciation; 5.

Or is a home with two units just a duplex no matter how small the second one is or if it contains appliances?

We're in the process of changing out the appliances, but we have been further advised that the cabinets therein also need attention and that prospective tenants have commented about it.

I am not going to provide these appliances. 

Make sure you're protected well with $500,000 (or $1M) liability on the properties, make sure they're Replacement Cost (versus "ACV" or depreciated value), make sure you've got some personal property (appliances, window coverings, etc.) coverage, I always add in some 'additional replacement cost' as well as inflation guard too. 

The tenants still have power in the unit (i.e. other appliances and outlets are all working), but I don't want to neglect this and create a situation where a fire hazard may be present.My question is: is there any type of preventative maintenance (i.e. periodically add deox/other chemicals to support conductivity) or inspections I should be doing as landlord on the panel every so often?