Liquid poos/ grunting/ groaning/ passing gas - these are all completely normal.
Weight gain does level off at this point (or they'd be elephants by 12 months
If the poo is a nice yellow colour I wouldn't worry.
If it was green and mucousy that would be a warning sign as the green colour with the mucus indicates malabsorption or milk passing through the system very quickly or a potential lactose issue. The mucus in this case is sometimes frothy. The frothy green poo can also happen when baby has a virus too. Bloody and mucus is also clearly not great news and that can be an indicator for a bf baby with a food intolerance/allergy.
You've checked with your doctor. I don't think you should worry. Potential food allergies in a ebf baby are very rare and you'd be seeing other indicators:
If a breastfed baby is sensitive to a particular food, then he may be fussy after feedings, cry inconsolably for long periods, or sleep little and wake suddenly with obvious discomfort. There may be a family history of allergies. Other signs of a food allergy may include: rash, hives, eczema, sore bottom, dry skin; wheezing or asthma; congestion or cold-like symptoms; red, itchy eyes; ear infections; irritability, fussiness, colic; intestinal upsets, vomiting, constipation and/or diarrhea, or green stools with mucus or blood.http://www.kellymom.com/babyconcerns/food-sensitivity.html#signs
She wouldn't be happy, easy-going but possibly described as 'colicky' and you'd certainly see more signs than you are IMO.