.Sounds like you have an Iron and or Sulfur Bacteria problem, or a natural sulfur problem. What you are smelling if hydrogen sulfide a byproduct of the growth of these critters. This can be especially present when the home has been unoccupied for a while, they love stagnent water, it also allows the gas (H2S) to concentrate. You need a good well cleaning and disinfection, see the link below. I addition to reduce the generation of the H2S you may want to eplace the magneesium anode on your hot water heater with an aluminium anode.
www.ironproblems.com