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Neon tetras can be fairly delicate. I see on your profile it says you just got them (don't know when you updated that) but it may have died from stress of moving tanks. I generally lose a couple neons or cardinals when I add them to my tanks. I'm also worried about your ammonia level, if you're cycled it should be at 0 unless you tested immediately after a water change and you have ammonia in you tap. How long have you been cycled and what are your normal parameters?
Use an actual computer and click on User CP in the upper left corner, then go from there.
Yes a dead fish will up your levels, but now that you've taken it out and it's been a good while you should test again and post your results then go from there