As I recall, when we started using Colorado River Water ( in Tucson, AZ) there were a lot of pipe problems because of the "Ph" of the water.
I know pinhole leaks in copper (especially horizontal lines) is of a particular problem because of "Ph".
1) I would have your "Ph" tested (your water company should provide a list of chemicals in the H20 as well as "Ph" on a periodic basis.)
2) You MAY be getting H20 from a different well than your neighbors.
3) If the same well, I'd look to see what your H2O lines are made of.
If black or galvantic pipe they may rusted (on the inside) and dumping rust into your tank.
4) Maybe getting a dialetic reaction. Are you using dialetic nipples (plastic coated) -- or -- copper fittings (not brass or stainless steel) to galvanized fittings or to the tank?
Some research seems to indicate improper electrical grounding of the house contributes to tanks rusting faster (causes these dialetic problems)
5) That said, all H20 Tanks rust inside, and maybe your neighbors have bought a 12 to 15 year tank, where yours is just a 6 year tank.