It is processing the ammonia. Your ammonia reading is zero. The issue is that it is not processing the nitrite fast enough. These are separate species of bacteria. They have different needs, reproduction rates, etc. In general, the A-bacs are easier to cultivate, but easier to kill off. The N-bacs are slower in reproducing, but much hardier. This is time well spent, although frustrating. We've all been there.
There is so much that we still don't know about these bacteria. The fishless cycling method is relatively new to the scene, but it is effective and a properly done fishless cycle is far less prone to future mini-cycles than fish-in cycling. Think of it this way, fish-in cycling can take 6 months or more sometimes to reach your ultimate stocking goal for the tank. Meanwhile you are performing daily (sometimes twice daily) water changes during that entire time. The fish are stressed due to elevated ammonia and nitrite, and so are you... the entire time. On the flip side, with fishless cycling, you can fully stock your tank in one go, if you so choose, although most aquarists start smaller than that. I started much smaller, but have since built up to full capacity. I'd like to add some more fish, but without another tank that is impossible. I'm happy with the ones I have. I just wish I had some apistogrammas! They are some truly beautiful fish! If you complete this process, your tank will be ready for the full complement of fish and you don't have to worry about ammonia/nitrite. You will still have to deal with an immature tank, so don't add any of the more sensitive species.
This process takes time. Being a fishkeeper requires patience. Keeping fish is very different from other pets. Other pets live in the air that you do and their waste is always kept separate, so it can easily be disposed of by the keeper. Fish, on the other hand, are very different. They swim in their waste. But, the good news is that you never have to pick up poo while enjoying a nice stroll around the neighborhood.
Any no one ever complains that your fish were barking all night keeping people awake, etc. They require minimal input from the keeper and provide a proven tonic to high blood pressure and stress. Its a pretty sweet deal, really. The problem that you are having is that you haven't gotten over that initial hump yet with all these tanks. Most people don't start with 3. Its usually just one. You are an extreme case of MTS (Multiple Tank Syndrome). It usually takes a few months or years of fishkeeping before someone goes out and gets a second or third tank. You started off that way!