New to plants...need help

Hi all, I started my first planted tank two days ago, and I thought I did everything correct, but today I started to see brown leaves on my plants so I did a water test (which everything was fine two days ago...I took water from my cycled 20 gallon to fill my new planted 2.5) and now my readings are

Nitrates 200
Nitrites .5
Alkalinity 80
Ph 6.4
Hardness 425
Ammonia 0

When I put the plants in I moved 2 of my red tetras that were in my 20, should I have not done that? Should I move them back? I'm using Plant Gro for food, they had 1 dose when I set up the tank. I'm using washed play sand and a thin level of aquarium gravel/rocks for substrate. There is a 15W bulb that has been on about 12 hours a day for the past 2 days. Oh, and my plants are a Broadleaf anubias and a Pygmy chain sword, and then some moss-like plant that's needles/leaves are shaped like pine cones (sorry, I can't find a picture of anything that looks like it)

I'm know I need to do a water change ASAP, but I'm curious why my Nitrates have spiked so high so fast..what did I do wrong? Thank you to anyone who can help...

Plant Gro is for aquatic plants. the problem must be not having enough bacteria in the tank, I just did a water change and squeezed my cycled tanks filter into the new plant tank. My fish are all alive, and I don't know if my plants are rotting, they don't look like it, it's just that my nitrites are ridiculously high - it's probably just starting the cycle over in a new tank and it's unrelated to the plants..I think?