I have a mystery regarding trip switches. The 2 switches that I isolate when the problem occurs the 2 breakers does not trip individually, The main breaker trips all the time which is on a different circuit. Look at the attached picture. Arrows on the top shows the 2 breakers that I isolate and on the bottom shows the main breaker that trips all the time. By me isolating the 2 top breakers the rest work ok and no more tripping during the night. During the day where I have most of the electrical appliances working and don't experience any circuits tripping.

At nighttime when going to bed the 2 circuits keep tripping. These are the outside outlets and the perimeter fence lights although these 2 circuits are not in use

During the day I can use these 2 circuits and don't experience any tripping. I purposely used the perimeter lights and outside outlets during the day and they don't trip . They only trip at night even when not in use.

I have rattled my head to try and carry out fault findings with no results. Could it be that the breakers have weakened but then again why not during the day