Red in chicks poop

[ChickPixie]

Hi there!
I have 6 week old girl, she had two brothers who recently got taken to a farm. I got two 7 week old girls yesterday from the farm to replace them. They are all getting on fine but this morning I noticed a few poops had red in them.
Here are the photos... I'm worried...

 

[hnichols]

This is perfectly normal. They are often pooped out overnight.

http://chat.allotment-garden.org/index.php?topic=17568.0

 

[ChickPixie]

 

[ChickPixie]

 

[ChickPixie]

 

[KatieRice]

I picked up three Wyandotte chicks this morning at a chicken swap, they are about three weeks old. They haven't been on medicated feed but I just started them on it when we got home. They all seem to be acting normal from what I can see (this is my first time having chicks). One of them just passed a stool that looks like this and I'm wondering if I should be worried.