My experience is once your nitrites hit zero your nitrates will finally peak and then start to come down. I found you may see another nitrate spike in a little bit and that will be the completion of your cycle. Water changes during cycle has a lot of opinions. I was attempting water changes initially, but after working with my LFS I decided to stop because we felt changing the water was not allowing the water to finish leveling off at the tail end of the cycle. It does not appear that you have added fish so just let it run it course. Waiting for the cycle to complete is frustrating...