Diagnosis
You probably didn’t flush the new filters long enough, especially the carbon block filters and the alkaline filter. The carbon fines and mineral fines from the new media need to be purged completely.
How to Fix It
You need a full system flush. With all new filters installed and housings sealed, turn on the faucet and let it run. Don’t just run it for a minute. For a full set change, run it for a good 20-30 minutes minimum. This purges the air and all the loose carbon and mineral particles from the new media. The water might look gray or black at first—that’s normal. Let it run until it’s perfectly clear. Then, fill a glass and taste it. It should be back to normal.
If That Didn't Work
Double-check the order of the filters. The RCC7AK order is: 1. Sediment, 2. Carbon Block, 3. Carbon Block, 4. RO Membrane, 5. Inline Carbon (post-filter), 6. Alkaline. If you put the alkaline filter in a pre-filter spot, you’ve ruined it and it’s contaminating the membrane.
Heads Up
When you change the RO membrane, you MUST use the new, correct flow restrictor that comes with it (usually color-coded). Using the old one with a new membrane can cause improper pressure and terrible taste/performance.