says, if the plants are happy and you're happy with how they are growing and looking, then you are good to go. That being said, I find it odd that your nitrates are so low. The API test for nitrates is known to be quite finicky at time. Have a look at your bottles and make sure they aren't expired. Also make sure to shake the heck out of bottle 2 before adding drops. It can make a big difference.
Follow up question, how big is your tank? It looks really nice!