Black sediment in whole house filter
We are on a 115 foot deep well put in 12 years ago, submersible pump, pressure tank, whole house sediment filter using polypropylene wound cartridge, water softener using standard salt, then cold feed to the house and feed to electric hot water tank that then feeds the house. Replaced hot water about 8 years ago, and replaced the rod a year ago. All is working fine.
We have somewhat high iron in the water that the filter and softener takes care of. Have to change out the filter every 3-4 months when we notice diminished water flow or high iron coloring in toilets. It is always iron rust red.
Now the odd part. Noticed reduced water flow and increased iron staining, swapped out the filter today and it was BLACK. Not slimy, not smelly, had black particles in the filter casing, they are not hard and do smear, most of them but not all. Filter was black/ dark grey throughout. Have not noticed anything different in the water at any faucet or I use.
Is my pressure tank diaphragm failing? Well or water problems? Other ideas???