Some of ours react immediately like that as well, but they always come back to us right away to see if we have something for them. We have been hand feeding them since day 1. Plus, I have a number of rambunctious children who all like to crowd the brooder and sit in the pen with them (supervised, of course). All that handling, petting and feeding by hand has made them very curious about what we have to offer. Even if I am not feeding them, when I stand over them and talk to them, they all come over and look up at me.
But like I said, if I sweep my hand into the pen quickly, they do run to the corner. What helps is speaking to them first, we make a "chuck, chuck, chuck" noise with our tongue to indicate treats and then reach in with food. Curiousity overpowers their fear pretty quickly. Even when we are catching them to move them, they almost line up to be caught now. Good luck!