how many gallons is ur tank? with 2 fx5 and a pro 3 should do the job and some. id prime the tank to get the ammonia down in the time being than flush the canisters with tank water and see if it stables afterwards. but yes it does sound like ur tank jump out of cycle. you can also try seachem stability works wonders for me.
125g one fx ,one pro3, I wonder why it Jump out of cycle
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