Does the water come out clear with NO color?
With the ph at 6.53 it would help to correct the ph either with calcite of soda ash injection and bring the ph to above 7.1..
If calcite was used it might help in removing some of the iron.
If the water had no challenges for the first 4 years and now it does , what if any thing has changed in your area?
There are any number of things that can get a well to change.
If you are getting 6gpm that is good, limits some systems or the size of them.. but that can be worked around.
Number of bathrooms and people in the home? numbers needed to help you size equipment for the treatment.