I'm trying to remember if you did one of theose Dr Tim's cycles. I do remember that you said you had 0 nitrates AFTER your cycle was complete, and I commented that you hadn't cycled then. Because you have not cycled your tank AT ALL (hence the 0 nitrates after you thought you had), adding anything that poops or dies will cause a spike in your levels and start a real cycle. Turbo snails do very poorly in nitrate and nitrites and will likely die, causing even more issues. corals also do poorly in ugly water and will probably die. your should get the corals and turbos out of your tanks and perhaps your LFS will hold them for you for 1-2 months while you do a proper cycle.
Or, after everything dies and then cycles, you can buy new stuff. Your choice.