Passed stool yesterday, dark plum colour?! could this be because i ate beetroot? today went and small amount of dark/black patches? is this serious?

It could be,get help: Blood in stool is a warning sign. Brisk bleeding warrants emergency care. Causes of bleeding may be predictable (e.g. rectal trauma), but evaluation is always appropriate. A rule of thumb (but not absolute): black stool means bleeding comes from upper GI tract; grape jelly stool from small bowel; silver stool from biliary tree; burgundy stool from right colon; red blood from left colon to anus.

Can't say: Eating beets can turn stool a reddish color. Red foods can occasionally cause dark stools. I am not sure what the black patches are from. Have you taken Pepto Bismol, Kaopectate iron supplements recently? Eaten any black licorice? Black, tarry, malodorous stools can be related to GI bleeding.