im so sorry to hear about your babies, i know how you feel, ive been there. the best way to avoid this from ever happing again is to get them from a well known hatchery. and myself personally i make sure that they are vaccinated for mereks and newcastle. cause you never can be careful if you get chicks from an auction etc. they may not have the out right disease but they maybe a carrier. had one that was a carrier and didnt know that at the time. but my prayers are with you.