Thank you so much for your answers - I have tested my municipality’s water, it has 0 nitrates and nitrites and is fairly hard. As for the test strips, I use the same test strips on my other two tanks and don’t get the same result as my newly set-up tank referenced in my original question.
A little history behind this new tank: I had a 5 gallon, heavily planted tank with snails and a couple of ghost shrimp. A few months into it my nitrates spiked really high and eventually killed my shrimp. I changed the water every other day, no food was going in and I removed any dead leaves immediately; but still my nitrates were high. After a year I took it apart, thoroughly washed the tank and equipment, added new gravel and added the same plants back in. This is now the tank where 3 days after doing this my nitrates are high again. Maybe it’s in the plants, since that’s the only factor that has remained the same? I don’t know, but I appreciate everyone’s suggestions. Thank you!