Cycling Issue

So He tank has been fine for around a week now, I'm finally going to add some more fish, should I get the numbers of cardinals up to 5 by adding 3 more or should I get some false juli corys not sure what should be the priority there.

Are the cardinals attacking the fighter because they feel threatened? If so surely a few more would be ok

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Or do I skip more cardinals and get some sunburst wagtail plattys