Aquarium re-cycling?

I've been having a hard time with my aquarium cycling with the nitrates for about 3 weeks. I went to the fish store and they told me to change a 1/3 of the water and i bought products called Stability and Bio Zorb to helo. When i tested my tank the nitries went back to 3.3-33(i use a tetra test kit) from 1.3 or somethn like that. I was wondering if this should happen. It is a 55 gallon aquarium and i have cut back on feedings