Well water issues

Here is my issue. We had a new well installed, and we have to treat for hydrogen sulphide. I'll describe our setup, and then give details of the issues.
Water enters house, peroxide injected, enters mixing tank, goes to the iron filter, then goes to carbon filter, then to the whole house. Back wash happens every 3 days, first the carbon filter backwashes at 0030, then the iron filter at 0300. We decided to go with hydrogen peroxide 35% and it does clean the water up nicely. However the morning after the back wash cycle the water has gone nasty, I can compensate for it by maxing the dosage of the peroxide and and once I flush it to that point its better again. Why is this happening after a back wash cycle and how do we correct it?