Its so easy to miscalculate as well as far as heights.  I didnt have a brooder set up for my babies when I first got them, so put them on top of the stove with the hood lamp on.  We keep the house about 82 anyhow, and so with that lamp on(with changing to a higher watt bulb) it was about 95 there.  The other two went right to sleep the first nite, but my other one jumped and peeped and hollered and was very insecure.  I underestimated her ability to jump out of a foot high box at 3 or 4 days old.  She jumped out and I came in to find her on the floor. 
She survived, thank goodness, but dislocated her wing and hurt her foot.  She is 8 to 9 weeks now, and still refuses to fly any higher than a foot, and is afraid of heights.  No one can tell me chicks dont remember things!
So sorry to hear bout your wee one, its so hard to watch them try to make it, and dont. My sympathies, I lost one a couple weeks ago and I still cry randomly over her.