Gen set

I was camping this weekend and notice that the plug in power meter was in the red right at 110volt's running the A/C and refrigerator. It usually in the green at 115 volts, Its a 7.5 KW Diesel 1994. back home now plugged in to my 30amp Im getting 115volts in the green running the same A/C and refige, and vac. Can anyone tell me whats going on and how to fix it? I will Appreciate ant help.