There's been a strong smell of sulfur, whenever we do laundry in the basement of our 3 story home.
Now I'm smelling it when the dishwasher runs.
Is there some kind of "flush" they can do for a whole house?

You may have a bad scraficial anode rod in your water heater. It is also possible for a bacteria to start growing inside your water heater requiring a chlorination rinse. I'd check the anode rod first. It's the plug on top of the heater but remember to shut off the fuel supply and then the fresh water incoming to the tank, open a hot faucet somewhere. You need a good socket wrench to remove the anode and it may be helpful for a large friend to be hugging the tank so it doesn't try to turn on you.