A chick is troubled if it's pipped but hasn't started unzipping AFTER 24 hours, or if the bit of exposed membrane around the pipping hole is starting to turn tan and dry. Well this is what happened to my duckling, I removed a small area around the pip and the membrane is white without any veins running through it. The duckling is still peeping and poking her bill out but has still not zipped 12hrs later. I have been put warm towels around the shell and placing her back in the incubator. In addition she pipped at the smaller end of the egg. Also, I just changed the wet paper towel and the membrane that's exposed has turned brown, she starts peeping alot as soon as she hears me.