An under sink filter might be your best bet, likely all the piping in the house is of galvanized pipe. Over long periods of time the interior of the pipes fill with rust. While flushing will remove some of the rust, you will be unable to rid yourself of it without replacing the piping.

Something like this mounted under the kitchen sink and populated with a carbon filter might work to clean up your main drinking water source. https://www.amazon.com/Pentek-10-Standard-Housing-Pressure/dp/B003VT7ERY/ref=mp_s_a_1_1_sspa?crid=1SEHOAUHR21TM&keywords=water+filter+10+inch+housing&qid=1677516610&sprefix=water+filter+10%22%2Caps%2C194&sr=8-1-spons&psc=1&spLa=ZW5jcnlwdGVkUXVhbGlmaWVyPUEyRFQ1RlZNSlpKMjE1JmVuY3J5cHRlZElkPUEwMTg3MDQxMklPUDNPTlVSRjJHNCZlbmNyeXB0ZWRBZElkPUEwMDk3OTE3MUpJQVpPSTJMNE9HSSZ3aWRnZXROYW1lPXNwX3Bob25lX3NlYXJjaF9hdGYmYWN0aW9uPWNsaWNrUmVkaXJlY3QmZG9Ob3RMb2dDbGljaz10cnVl

Have you verified that the incoming water is clean? Before you proceed further, you should get the opinion of another plumber.