Kapampa I've had at that size weren't fussy about pellet size, anything between 1-3 mm pellets and they were fine.
Don't know if this is your problem, but my kapampa never liked Thera-A, I gave up on it for them years ago. Pretty much any other NLS they like-- in fact, these days their only pellet is NLS and when they're hungry they'll beg to be fed. Different story with Thera-A, too much garlic for their tastes, apparently. I've known other people to feed Thera-A to moba, etc. with no problem. Other fronts I've had, some liked it some hated it. Back when I was trying to get the kapampa to eat it, the first few days they'd nibble at it, eat a little but not much. If I kept feeding it they'd get an attitude, stop eating and sulk, even hide-- soon as I went back to other foods, including other NLS, they'd go back to normal. They did this several times when I decided it wasn't that important to me for them to eat it.
I'd seen this before with fronts over the years, feed them something they like and they 're fine, feed them something they don't and some of them get an attitude.
I've had other fish that love Thera-A, rotkeil severums, for instance, and I've known other people to feed Thera-A to moba, etc. with no problems. My kapampa-- nope.