Maybe keep a closer eye on them for any odd behavior,Should I worry about the rest of the flock? Anything I can do.?
hard to do if you don't have the time.
Good feed and water, plenty of space, etc.
If she was a loner, she could have been ill upon arriving,
or picked on as low bird and couldn't take the stress.
It's possible she wasn't getting enough food/water.
Most flocks carry 'dormant' disease, showing no symptoms until stressed enough reduce immune system function.
I suspect that your flock is carrying something that the dead bird could not fight off,
or it was carrying something that the moving stress allowed to flourish and overcome.
There's really no way to tell what it was unless you have a reputable lab do a necrospy and pathology.
