adding LR to a small tank can increase diatoms but shouldnt effect trites or trates imo...
I have recently started a 10gal and during cycling i didnt wait long enough for my "good" bacteria to grow as large as the others and ended up with a lrg amnonia spike in the tank....everything was fine i just had to do emergency water change. This is wat i would reccomend doing....i do like maybe a 2-3 gal w/c just about every week and a half! Needed on such a sm tank imo, specially if u dont have a skimmer going on it yet!
After i did that 1st w/c btw everything caught up and was pretty stable!
Yep this sounds right, likely the tank was not cycled to the point that feeding the fish would be OK