Shut off the power to both A/C's. Remove the cover and inspect all of the connections. Check all of the electric connections from the panel box up to the A/C's. Tighten all screws. If all looks good then check the capacitors. Smell them. If they are bad then they have the burned electrical smell. If you do not know this smell find someone who does. If all checks out then you have reached your limit and need an experienced A/C tech.
When I bought my 5'er I had easy start kits put on both of the A/C's. This gives them a starting boost especially in low voltage conditions. They start the fan first then the compressor just snaps on 10 seconds later even if the voltage is a little low. This is a good idea for all A/C's including house central units. The kits for RV's are about $ 55.00 plus installation.
Ralph & Snickers
2006 3500 Chevy Dually - 8.1 - Allison
2006 30' New Horizon - Solar