He is gorgeous! I love foals.
RE the ratained Placenta. I recently had a cow that retained the placenta for 4 days, then spontaniously cleaned and was fine. She had a bit of a tramatic birth (pushed for over an hour with a large calf). We give our cows with RP 2-3 days as long as no signs of infection (tyed up if dragging), but other than that we leave them alone - no pulling on it, flushing, anything as long as no signs of infection (smell, green slime, puss, fever, runny nose, cough).
Truthfully, I would leave her alone and she if will clean on her own. The more you mess with it, the more chance of infection, and problems.
I was have a degree in pre-vet, speciliazing in reproduction and large animals, plus have lived on a large ranch for 10 years, so if you have more questions, I can try and answer them
I love horses from 0-2 and about 8 on up, but could do with out them from about 2-6 or 7