QEST (PB or PEX) is very smooth and rust doesn't build up much in that type material so you get the rust through it quite easily.
You need a water test on your water from as close to the well as possible, like at the boiler drain valve on the pressure tank tee. Test for iron, hardness, pH at least and Coliform bacteria would be a good idea, along with manganese if possible plus sulfates, chlorides and TDS (total dissolved solids). Then post the test results.