I would stop adding the "stress zyme" asap. Those chemicals can throw off your test results, so you may just be getting inaccurate readings.
My suggestion is to do a large water change, condition the water before adding it of course, then do NOT add the stress zyme anymore. Those are just wastes of money anyhow with little to no benefits in your tank. Or you could look into buying some bio spira, there's some info on it on my website linked below.