One week ago I got 10 new chickens about 7-8 weeks old. They joined my 3 silkies. 2 have since died. One showed no signs of sickness or problems just was gone when I opened the coop. Now this morning I went to let them out and another is dead but yesterday was not acting normal. Sleeping in the coop while the rest were out in the yard. The first was a silkie and 2nd an EE. Any thought? I'm worried about the rest of them.