Just do daily small water changes, maybe 5 gallons at a time. Monitor the nitrite levels. You need to get a test kit. If your buffering capacity is very high, driftwood will not effect the pH of your tank much. 7.5 is not a high pH. Just leave it alone, your fish will be just fine with it. My pH is 8.2 out of my well, never had a problem with keeping anything. Just get the ammonia and nitrite under control. If you had removed your filters, put them back on, after thouroughly cleaning them. Carbon isn't that big of an issue, I never use it on my tanks anymore.