120 Outlets showing only 24 volts when tested

It sounds like you have a ground somewhere. I think it is telling that all the outlets you have an issue on are GFI protected circuits. Are they all on the same breaker? Open the breaker to the bathroom circuit and see if all three go out.

Start by unplugging every single thing on the circuit and see if you still have the problem. Next, shut off the breaker, remove the GFI outlet, safely isolate the wires, turn the breaker back on and check the voltage again.