I raised a group of baby WC Yucao Orinos, all pellet slammers, since babies.
Sold off the first 3 no feeding problems. Sold off the next largest bully fish, kept the last 2.
The larger of the last 2 stopped feeding for almost 7-days, it would take the pellets and then spit them out. The slightly smaller fish would still eat but not as much.
I was sick about it, because the larger of the 2-fish was my favorite fish, but after a few weeks (still have the 2-fish) by themselves in a bare 90-gallon-tank, 1-fish aprox 9-inch the other around 8-inch there both back slamming pellets right from the bottom of the bare-bottom tank floor.