I have a 30 amp trailer and I use a step down to a 20 amp plug when I am in my driveway. I haven't installed the 30 amp plug in my garage yet
. I don't use the AC unit when I do this unless I have a thicker gauge cable as it will dangerously heat up the line and\or blow a fuse. Don't ask
So if you use a 50 amp plug converted to a 30 amp, I would only use 1 AC. The second AC unit is why you have the 50 amp plug in.
As you have heard from others, Be careful, Why did the 30 amp blow in the first place, you don't want to loose both power sources.