Propane appliances throwing orange flames suddenly and generator's back firing
Kris' comment is likely a good reference. Consider to perform a test by operating only one device. If the duration of normal operation increases, or normal operation continues throughout the test, it's an indication of too-low temperatures preventing the tank from allowing evaporation.

The backfire of the generator is another indication of insufficient evaporation. A generator takes a substantial amount of propane compared to other devices, increasing the cooling on the remaining liquid.

If you can operate appliances other than the generator, you may discover the evaporation level to be sufficient to continue.

Pouring warm or hot water over the tank will improve conditions inside the tank, but I don't have the math to determine how much heat has to be applied to accomplish continuous running of the generator and other devices.

Because the propane gets colder as it evaporates during use, the amount of heat you can apply will improve the circumstances of operation. If you can manage really hot water, you'll come out even farther ahead.

I can envision a "camp fire" environment, with a kettle of water. A hose running from a water source to a set of coils inside the water kettle will create hotter water for the propane tank. One does not really need the kettle, if one constructs the coil directly in the fire but hat may raise the temperature too high for safety's sake.

Using water as a means of increasing the tank temperature reduces the risk of overheating the tank to an overpressure release. 

The mention of ice freezing on the tank shows you how cold the propane is (and of course low ambient temperature doesn't help!) One very good reference mentions that 60°C (140°F) water is used to assist vaporization of the propane in cold conditions. We used to keep our hot tub at 100-110°F and it was pretty darn toasty, so you won't likely overheat the tanks.



According to the article on the linked site, propane boils at -42°C/-44°F, which tells you that the evaporation during use is causing the propane to chill itself below those temperatures!