First off welcome, back in time and Stormin to irv2.
Like Paul said you may have to trace your duct work into your storage compartments. If you find a tin foil 4" duct you have a start to correct your problem.
You may also find that you have 12v or 110v heating pads under your tanks. Most likely 12v pads.
If you have neither you have extra duct outlets from your furnace which can extend down into tank areas.
I have a heat duct off furnace that has a 12v wisper fan installed in the 4" foil duct which cycles with the furnace when it comes on and off. If you do have a duct you can add the 12v fan and install a switch near your dash to put on 12v fan that you will add in duct.
Some coachs have a winter pkg option when ordering coach which you may or may not have.
Your profiles are not filled out but if your coachs are new they should be under warranty and your dealers should be helping you.
At least you know what you may or may not have to pursue your dealer or MFG.