Ammonia is tricky....why not test again in am to confirm your zero to be safe. If you add CYA and the bacteria that converts it is still there, it might just turn into ammonia again, which might be what happened after the dichlor and why you have no cya reading right now when you started with 54.
I fought ammonia once in a foreclosure swamp. I didn't add cya at all until the FC was holding, and then things cleared up pretty fast (eg a week, but the FC held.)