Gaming desktops can use as much as 12-15 themselves. They don’t often, but they can add up easily. I’m willing to bet those are 15A circuits.

Elsewhere in the thread, OP remarked that much of the apartment is on two circuits. It’s probably ancient BX wiring. Unfortunately, OP is renting from one of Dan Greer’s cheapskate shell companies, who will never ever be convinced to rewire an apartment. The other issues seem more plausible, but they drag their feet hard on anything.