Cycling- high nitrate spike

[fraoch]

Hi Everyone!
I am just getting back into the hobby after a few years away and I am setting up a new 160l.
I started a fishless cycle with ammonia roughly 2 weeks ago and decided I would also try out adding the Nite Out II bacteria in a bottle to see if it made any difference. My ammonia level was constant at about 5ppm for just over a week then I saw the nitrite level increase to 0.5ppm and the ammonia drop. I have continued to add ammonia each day to keep it at about 2-3ppm. Today when I tested the ammonia is back to 0.25, nitrite at 0.25 and nitrates at roughly 100ppm- hard to tell because the API test kit doesn't do specific readings that high.
My questions are:
Does this mean I am nearing the end of my cycle already?
My tank is already planted- should I do any sort of water change with the nitrates being so high or just leave it be?
If the nitrates keep increasing will it start to slow down the cycle as a whole or kill off the bacteria?

Thanks so much in advance for any advice!

 

[fishwonder]

Since you have plants and are trying to cycle it may not work and give false readings since plants eat ammonia, nitrite and nitrates. It may take 3-8 weeks to see an outcome.