It seems your already cycled tank somehow had the cycle crushed. Clean the filter media should be done very carefully, otherwise its bacteria colony can be damaged and thus crush the cycle. Fishless cycle can be rather quickly (with a few days) when you use heavy seeding products combined with pure ammonia. If I were you, I'd try to have the tank cycled as quick as possible either with fish or without the fish.
If you decide to do fishless cycle again, I believe you already know the process. Make sure the filter is working properly first, then add ammonia, and a whole bottle of bacteria product.
If you decide to cycle with fish since you already have them, the process can be done fairly similar without the part of adding ammonia since the fish is a source of ammonia.
If you choose the latter, you can use Prime water conditioner for daily partial water change which will turn the ammonia into harmless ammonium temporarily.
