HI!! The pet stores are telling me all kinds of different things

!! All of you were so helpful last time, I thought that I'd come back here.
Swimmey seems to be doing well. He digs around in his gravel a lot, ate the second plant that we bought him and is now working on eating the first plant. He has not touched plant #3 yet. Since it was so hot here, I've been adding ice packs in his tank to keep it from going above 80-degrees. I bought a tank divider and put the divider about 4" away from the edge so I could place the ice pack in horizontally and not take up a lot of the surface air. It's starting to cool off so I shouldn't need that much longer! Anyway, he looks pretty healthy and does not show any signs of sickness.
I still have the Jungle Sticks but discovered that their Nitrate/Nitrite levels are a little off. So I'm not really using them but will use them to check the chlorine or for a quick check mid-week. I bought the API Freshwater Master Test Kit and used that to check the levels tonight. I also have syringes for accurate dispensing. I have not changed any of the water for 7 days and am planning on doing that the next morning. The last time that I used the gravel cleaner was about 2 weeks ago and that's near when all these problems started. (Perhaps I cleaned it TOO well?)
HERE ARE THE LEVELS
pH: 6.8. (I added 0.70ml of API pH increaser, since goldfish prefer 7.0-7.4. Last week, it was at 6.2 but increased after I added 1.0ml of the pH increaser.)
Nitrite: 1.0-1.5 (it's in between the two colors on chart. This is the same as last week.)
Nitrate: 10-15 (it's in between the two colors on chart. It was 160 last week!)
Ammonia: 0.0 (this is the same as last week.)
What do you recommend to get the Nitrite levels down? Should I put the Nitrazorb back in the filter?
Background Info, if you want it:
After PetsMart's recommendation, I used some AmQual Plus to bring down the Nitrate/Nitrite levels but that did not help. I got an in-tank monitor for the Ammonia levels and that showed the Ammonia was at Zero. (I also have the in-tank pH monitor and both of the in-tank monitors match what the API test kit reads.)
I tried large water changes (waiting 2 days between each: 70% then 50%) but that did not help.
I went to Petland Discounts because the clerks seem more knowledgeable. The clerk said that the tank could still be cycling but when I told him how high the Nitrate/Nitrtire levels read, he recommended adding Nitrazorb in the tank's filter. (He told me to do a 10-20% water change before adding it but not another one for a week bc I am removing the beneficial bacteria.) After 3 days, the Nitrite/Nitrate levels still showed high on the dipstick. So, I brought the water to a local Pet Store and PetsMart. Both stores had similar readings and showed lower Nitrite/Nitrate levels than the dipsticks had. The guy at the local pet store told me to remove the Nitrazorb. When I got home with the new API test kit, I tested the water myself and it was pretty close to what they got in the stores so at least there is consistency!
THANK YOU IN ADVANCE!!
