Hi, I do not know any other details about your cycle, but it sounds like you might be entering the nitrite phase. Please check the "do and do not" link in my signature and read the "tweak the cycle part".
You still need to be adding ammonia but at a reduced concentration of about 2ppm. This is to encourage the Nbacs while still feeding the Abacs. When you see the Nitite drop to zero then up the ammonia again to 4-5ppm. When the Ammonia & related Nitrites are consumed in a 12 hour period you are entering your qualifying week.
When your filter eats ammonia & nitrite in 12 hours for a 1 week period you are ready for fish.