My kids stool is black in color - what could be the reasons?

hi friends..
my kid is 2yr and 3 mnths..she is a very bad eater.she loves to have milk but dont take any veggies..likes fish..so if i give her fish she'll have some rice for lunch..owise no way..she'll have a glass of milk & a small khela for her breakfast..thn i use to give her"navdhanyam".or raggi(that too in bottle..).im very much worried abt this bad eating habits..so frm day b4 yesday i started giving her carrot juice mixed wth her milk..and when i make porridge (raggi..)i make some veg soup and mix it with this..its okay with her..she is having this things wthout hesistation.but frm yesday i noticed colour change in her stool..its lmost black incolour..is thi coz of carrot juice..?is it okay to do like this..??is there any way to make her eat food pply..plz give me some advises regrding this...