Just retested my nitrite is a tinge darker than baby blue, so for sure >0.25 ppm Nitrite. Ammonia 0 Nitrate 0 Kh 12 Calcium 400-500 PH 8.2-8.3 Phosphate still 2.0ppm.It is hard to tell from your picture of your test kit of what tube is for what test.
It looks like you have ammonia and nitrite. Those should both be 0. Poor water quality will cause fin rot.
I think you overloaded your tank too quickly and it is going though another mini cycle.
New tanks are tricky.