Check you hemogram,if there is  low Hb plan upper gi endoscopy,could be ulcer bleed

Usually these medications don't cause black stools Black stools is mainly due to 1. Dark coloured Food intake ( like green leafy vegetables- saag, dark chocolate- large amount, other dark foods over fried food, carmelised food, etc -- but in such case colour of stool correlates with colour of food) 2. Iron supplements - un-absorbed iron 3. Gastritis/ GI ulcers  with internal bleeding mild to moderate. There are other minor/ rare reasons as well

Could b due to tabs