Chicks about to hatch - help needed with incy

WE have had 4 altogether, the first 2 were fine, the 3rd was a bit weak and wobbly - tried to feed her ( we call them all her - in  hope!) with egg yolk and made sure she had water, she has started eating by herself, but her legs have splayed out, so the poor thing is now braced! She is still smaller than the others but we have our fingers crossed.   The fourth hatched after 26 days but it just laid there , tried to move but couldn't it was so weak, tried to feed and water it but afet 3 days it had not moved and seemed to be suffering - so we put it out of it's misery. 
I know have 11 more eggs to try, I had a few problems with the humidity  and temperature with the last lot, so I hope it will be better this time.