Is it normal for my chicken to be pooping poop that is blackish purple and somewhat runny?

im really worried that my pet chicken has something wrong with her on the inside. its been a little over a month that she has been pooping that way.. its blackish purple and sometimes its either runny liquidy or hard tiny turds.she acts normal like she always has been and im wondering is she healthy or should i take her to the vet? her diet consists of rice soy veggies sometimes fruit bread chicken feed and while she is grazing on our front yard bugs like worms and grasshoppers some grass and bowl of water . can someone help me find out whats causing her to be pooping blackish purple????