You need to spend as much time with them as possible. Take them out alot, hand feed them a lot, etc. If they get skittish as they grow, (which happens often) you could try putting them in a smaller cage and then putting your hand in there so they have no where to run and will get used to you...
How friendly are your chicks? Button quail are known to be very skittish if they are not tamed as babies. My adult buttons will eat from my hand but they freak out if I try to touch them.
Yea its hard losing them. I had 7 button eggs in the incubator a few months back. Only 1 hatched he was so friendly and then he died and im not sure why :(