I would start by having the batteries tested to ensure they are not done.
Second, as already mentioned, would be to sort out the charger and ensure it is doing its job correctly, and replace it if nessesary.
While going through the charging system check all of the wiring connections starting at the converter all the way to the batteries, including the junction box where all of the wiring ties into the trailer.
Our previous 2016 trailer was absolutely deplorable. The wiring was so bad that the brand new dual 6v batteries wouldn't charge enough to make it half way through the night. that included running the gen for as many hours as the sites would allow and also included about 4-5 hrs of sun on a 260w solar system. I'm really surprised that the trailer didn't burn to the ground the first week we used it.
As far as solar goes, 200 watts is a great start, and will at very least decrease the amount you have to run your gen... If you are a power miser and get alot of sun this might be enough to keep up with your power consumption.
We currently have 2 225 AH GC2 6v batteries, a GoPower solar system with a 200w mono panel, a 30A PWM controller, and a transfer switch with a modified sine 1500w inverter (it will be changed out for a pure sine in the near future).
This system works well for us but does not cover our power needs, so we do run the gen for a few hours every 3-4 days.
On our previous two trailers we also used 2 6v GC2 batteries with the EPsolar, EPever 20A MPPT controller's with remote displays and 260w of mono panels.. This was also a great system that gave us zero issues.
The difference between the two systems for us was not really very significant as we didn't use 24v panels to take full advantage of the MPPT.