I've been running 2 ac's on 30A at my house for weeks now in 90 degree weather. Like others have said, watch what else is being used as 2 ac's on 30A is close to the 30A limit. I also suspect a weak power system in the campground.
Another thing to look for is dirty, corroded, are weak contacts in your plug connections. Dirty, corroded, or weak contacts will add resistance in the line, resistance will drop more volts as amps go up. Sometimes cleaning the contacts will help if you are on the edge.