[animal mad]

I am currently hatching 20 silkies it is day 22 and i have had 16 out no problem at all the humidity it 75-80 %, today i have had a problem with the membrane inside the shell getting really sticky so the chick can not get out. one hatched out and kept getting stuck so i have washed him and now he seems fine. another one has come out and the same thing really sticky any ideas, not really had a problem before.