cause for baby chicks that can't walk?

[oldcluck]

I need some help from the incubator experts. I just hatched 24 of 36 fertile eggs in my genesis incubator. I left it at factory set temp of 100. I kept humidity at 45% raising to 65% at last 3 days. Of the 24 chicks 4 were unable to keep their legs under them and had to be culled. I am not a complete newbie at this and am aware that slick surfaces can cause spraddle legs but these chicks were on wire in the incubator and on cloth in the brooder. I noticed the chicks had this problem as I took them out of the incubator. Other chicks are doing fine.Chicks began hatching on the evening of the 19th day so i think maybe the set temp should be moved to 99.5.
Does improper heat or humidity cause this problem? Should i have pulled a vent plug? Any input appreciated.
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[deserthotwings]

Sounds like you had it all set perfect. I don't have any answers but would sure like to hear what the experts say about this.