so sorry to hear of your loss
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i am not chicken wishper but here is a few thing to look into frist if you have a heat lamp was it a clear one if so i would go to a red one ASAP! this will calm them down . then i am sure they had plently of feed an water, they get board so i would get a flock block from
tractor supply about $12.00. get some brocclie hang from a string so they an peck at it also carrots cabbage thing like that.
check the list of things not to give chickens on this site very informational .
also do you have plenty of room in the coop they get a little crazy if not enough room i use about 5sq fet per bird if not more.
also what feed do you use some times if the protein is to low they will get like that. i use KENT e-xtra egg and mulitiflock i like it.
have you check for mites or lice that can cause some stressed out birds.
as for worming i am sure that would not be a factor but some thing i would get done once they are clam agian wait a while. i have 118 birds and i have some chicks of different ages it is some time diffcuiate to intergrade them all to gether in the winter, i wait till they are all about the same size i dont have to much problem then. some times there is just that one who thinks they need to beat on every one so we have a nice little pen always set up for that chicken time out as we call it after a day or more they get the message are glad to be back in the flock
i hope this helps and you dont have that problem agian. if it just one bird that is the culpert you might need to cull it
i had a leghorn that just kept picking on one of my younger chicks she would find any way of getting to her.she put a hole in her head so needless to say she is no more but after a few stitches cinder the chick is well not sure what happen but i will not keep a bird with a bad attuide. she did not look sick some times they just pick on the weak but i saw not sign of that . i think we just got one mean leghorn
good luck !! and dont get discourage it will get better.learnig about them is half the adventure!