[TinaTheGhost]

I am new to aquariums (other than what my family had growing up), and I am currently cycling a 20 gallon long that is planted with a focus on low light, low temp, plants because it is to be a future axolotl tank. I use sand substrate and the rocks you see are seiryu stones glued together using aquarium silicone that have been fully cured before attaching java and placed into tank. The stage in cycling is showing signs of nitrates at 20 ppm (6th week or so). Although, I've checked for the past 2 days and I still have so much nitrites and was wondering if it's supposed to take this long but I am aware the second batch of bacteria are slower growing.
I suddenly started noticing these ashy, black/grey, substance on my substrate along with white/grey substances on my plants. With the power of google I could only come up with "diatoms" but I am not expert enough to confirm this.
There may be contributing factors. I added 2 Marimo balls and started dosing with Ace Hardware Janitorial Strength ammonia (reaching for about 4 ppm). I started off cycling with fish food flakes but it was so messy that I went out and bought pure ammonia instead. The mysterious substance appeared later that day. I started cleaning it out with a turkey baster at first but more and more keep appearing. I hope someone can help identify and give me tips on resolving the problem!