My 4 week old has had green frothy poo for about a week. She's gaining weight, and doesn't have any fevers. I BF exclusively, and make sure to drain each breast and not swap between feeds. I've tried block feeding the past 3 days, I've swapped to a lactose free diet, and her poo has shifted from green and frothy to green and slimy. I'm worried it's been over a week now that she's had runny poos. Any advice?