I just moved into this house and still can't figure out how all the stuff works.

The question: in the basement there are kinda 3 electric light areas, like kinda accent lights - all regulated by 3 separate switches. 2 areas always been giving this dim light and only the center area been lighting up bright. It was my understanding that the difference between the dim and bright areas was the wattage of the bulbs - like let's say 45W and 65W - I can't check it 'cause on most of the bulbs there are no markings.

Today however the central area went dim. There are no dimmers in the area that could've been accidentally triggered.

What could possibly be the cause of this sudden dim and how to fix it?

Thanks a lot in advance.