Am I starting new tank syndrome all over again?

:( Sorry but yes the cycle did restart most likely, you removed the source of ammonia, the stuff the bacteria feeds on. Although it is possible there is still some beneficial bacteria, to feed it put in a small amount of fish food every 12-24 hours. Try this and test your water to see if ammonia has been converted to nitrite or nitrate, if you find any traces of nitrite or nitrate the cycle has started where it left off. Don't wash off decor unless it's an emergency as decor is a home for bacteria too. Because of all the water changes you may have eliminated to ammonia which ended up starving the bacteria. 90% chance you restarted the cycle, you'll need to test the water to make sure. Okay, for your stocking, corys need to have a partner, 3 corys is better though, 6 is best. A rubber lip is good but that gets big for a 20 gallon, 8 inches and messy. You can get a bristle nose pleco though. African cichlids could be in there but you need to have them by themselves and get Electric yellow or kribensis. Google these fish to see if you like them. Mollys would be good with corys, dwarf gouramis, corys and a bristle nose. Hope this helps!