Your lights are 12VDC and run from both your converter/charger unit or the battery. Sometimes if the battery is going bad the converter/charger is trying to keep up with it and power surges.
The first thing to do is check the fluid levels in your battery. If one cell is empty and the battery case is warm to hot then you are probably experiencing a failed cell in your battery.
You can also disconnect your shore power connection and read the DC voltage across the battery terminala... It should be around 12.5-6VDC for a charged up battery..
If you battery is reading below 10.5VDC then it may be toast now...
Roy Ken