Update!! Did a major water change and a few days later the levels were a lot of better, a completed cycle...however, one problem.
Bought a gobie and a tang today, since the cycle finally completed because I only had just a clownfish and two snails. gobie is fine but on the way back from buying them the tang started to act weird, laying sideways in the bag, however, I've read online they do this when they are stressed, so it may have been normal. I added it into the tank and it seemed fine for a little while but it would sometimes stop and lay down or lay on something for 10 minutes, get back up, and do it for awhile. Just about 15 minutes ago, after being in the tank for a few hours, it died.
But why? All the levels were okay. no problems with temp, salinity, pH, no ammonia, no nitrite, and a healthy amount of nitrate, and I watched the fish for some time at the store so I'm fairly sure it was good. The store was somewhat far, it took me about 40 minutes to get home, would that have an effect? I'm just really curious as to why he hid in a hiding spot and died. The other fish is just fine too...