They are older Boston speakers from a prior computer
They are either failing, the dishwasher is at fault, or poor grounding issues. If you can find a local Ham operator with a EMI/RFI meter, they can tell you if the dishwasher is at fault, along with you need to go back and recheck all grounding, to make sure that it is properly grounded to Earth ground.
As I also stated before, a good Surge protector (does not have to be a $500 or $1,000 model, there are good ones out there for under $50), can also help with this issue, by helping to suppress EMI/RFI noise injection into the electrical system.
__________________ Ren: Now listen, Cadet. I've got a job for you. See this button? Ren: Don't touch it! It's the History Eraser button, you fool! Stimpy: So what'll happen? Ren: That's just it. We don't know. Maybe something bad, maybe something good. I guess we'll never know, 'cause you're going to guard it. You won't touch it, will you?