TMI toddler poop

My 14 month old daughter struggles with harder stools, has since we started solids. We've tried everything from fiber rich foods to natural remedies to Miralax (suggested by dr). She usually will poop once a day or once every 2 days but they're typically harder and she strains a lot 😣

. Today though there were several black pebbles mixed in with her poop. Is this just normal for constipation? It wasn't undigested pieces of food either from what I could tell, they were just very hard and dry dark balls.