I still cannot tell a thing about nitrite from that picture. It is not close in color to any of the bars as far as I can tell. In fact I would say I cannot see any difference in the color comparing all the pictures you have posted for nitrite. It is almost as if the light is too bright. The ammonia test is similar re color. The best I can offer is it is low. Nitrate looked like 40 to me.
I just realized that your pictures include the Nitrite bars 4 times. I count the other tests where the nitrite bars are also clearly visible. take a look at the color of the nitrite bars in each of the four pictures. No two are alike as far as I can see. You need to figure out how to get an accurate reading on your end as pictures are not helping me to have any idea of what the result is.
We are starting to go in circles with pictures and what you report about nitrite. I can only make two suggestions. One is to take a fresh water sample from your tank to your local store and ask them to test it and give you their opinion. The other is to get a different brand of Nitrite test kit and try that.
I suppose we could try to coax a diluted test by reducing the number of drops. The problem is you have to work in 20% increments since the test uses 5 drops. Therefore, here is what you would do based on how many drops are used. It assumes that as you reduce the number of drops you get a color match of which you are certain. The problem is the fewer drops used, the less accurate the result can be because we are working with pretty small volumes of water and drops can vary in size a tiny bit. Using more drops would tend to even out the potential variability. I suggest you start with three drops and if that doesn't help retest with two drops.
Use 4 drops and divide the result by .80
Use three drops and divide the result by .60
Use two drops and divide the result by .40
Use one drop and divide the result by .20
I am not even sure if doing the above one step at a time will end up giving you a color about which you feel confident.
I actually went to the Wichita water site and then also researched what might mess up a nitrite test at Hach.
Strong oxidizing and reducing substances interfere with the test. Cupric and ferrous ions cause low results. Ferric, mercurous, silver, bismuth, antimonous, lead, auric, chloroplatinate and metavanadate ions cause a precipitate to develop.
The water report did not mention iron at all, but it did indicate a low level of copper. I doubt it is enough to be an issue also it is the ionic form that interferes.. Although the report was published in 2020, the testing for it was performed in 2019. So the data is not really current. The only reducing agent that you have added to the tank would be the dechlor, and that was a while back and the effect should be long gone.
I am not giving up here. I like a good challenge. But until we can get a reliable method for you to test nitrite levels......... However, I can say for sure that you have established some level of the cycle as ammonia drops and nitrate is produced.