If its sick or weak the other will kill it, maybe the better thing to remove it or try turning it again, last thing you want the kids to see is it getting killed, its not that bad to open an incubator, just spray warm mist of water back in after to keep the humidity up, the rest will be fine i remove all mine as they dry and the rest always hatch. i think we all go 2 fare with this lockdown rubbish myself, not like a hen sitting on a nest can lockdown the day her chicks hatch, if it cold then its cold, if it hot then its hot, she just has to deal with it the day they come,its hard to watch a chick that's not doing too well if it deformed then the next stage will be even harder for the kids you may have to cull the bird. sorry but it may come to that