Nothing you mention sounds like a source of nitrates to me (especially since your nitrite is high, and it should drop when nitrates rise). What type of test are you using? Dip strips are notoriously inaccurate, so you need a good liquid test if you don't have one yet. Many people use the API freshwater master test kit. Fair warning, the nitrates chart on that one is hard to read: The colors over 40ppm look practically identical.
If you're already using the API test, you could still be getting inaccurate results if the test is expired or if it's been sitting a while and you didn't shake/pound the heck out of Bottle #2 to remix the reagent before testing. Seriously, smack the bottom of that bottle on a table edge or something several times, and then retest, following instructions about all the shaking/mixing, etc. And be sure the read the test at 5 min, not 10 minutes or an hour later. (No offense. You probably already know that. But I read posts in forums like this all the time from people who get confused because they keep reading the color results for hours, as the color keeps changing.)
If you're already using the API test, you could still be getting inaccurate results if the test is expired or if it's been sitting a while and you didn't shake/pound the heck out of Bottle #2 to remix the reagent before testing. Seriously, smack the bottom of that bottle on a table edge or something several times, and then retest, following instructions about all the shaking/mixing, etc. And be sure the read the test at 5 min, not 10 minutes or an hour later. (No offense. You probably already know that. But I read posts in forums like this all the time from people who get confused because they keep reading the color results for hours, as the color keeps changing.)
