Try feeding them a wet mash made from feed and water. If they eat it like vultures, grind your crumbles smaller. My first Polish died of starvation on day 5 because the crumbles were too big. Then I noticed my second batch of Polish looked like they were eating, but they weren't. I ground the feed and they ate like vultures.
I'm not saying this is your problem, but at least it's an idea.
I'm not saying this is your problem, but at least it's an idea.