In that case, I would mostly try to reduce waste going forward, but not try too hard to make them eat the spilled feed.
Moving the feeder to a different part of the brooder may help a little bit, because then the spilled feed is not right under the feeder, so they are a little more likely to...
It would probably be safe enough to take the feeder away for an hour or so, maybe once or twice a day, to encourage them to eat the spilled feed.
But I would not do much more than that.
Overall, it is probably better to consider that feed permanently lost, and try to come up with a way to...