What you are seeing is genetics at play, not some kind of voodoo FH food magic.
Only reason i recommended that brand is because that's all I've ever used.
No issues health wise as of yet. (knock on wood)
Got that CLEAR on deck just in case.
I'm going to contradict my last statement only because i mix Hikari Blood-Red Parrot+ as well. Mainly use Okiko tho. May give the NLS a try. I use NLS in my reef. FANTASTIC brandWhile there are more premium brands like NLS, Northfin etc. I personally would put Hikari way above Okiko, you might try some to give your FH more variety. Would suggest Cichlid Gold, Biogold+ & Bloodred Parrot+.