The mama hen does protect them from the older chicks, but to be safe I would move the chicks and her for the first week at least just so mama can get back on her feet and ready to protect her babies. She should be fine to go back in with the flock because they can still see her.
I am not a duckling expert, but I would separate them, and add brewers yeast to there feed. This helps them grow right. I would do the corrid with the chicks, as ducks do not need the help. Also, if you are comfortable with using medicated feed I the chicks for a little bit, this should help...
That does look like a bloody poo. While it could have something to do with the hen losing feathers, it could also be cocci. This causes bloody poop in chickens. You should be able to find something called corrid at a feed store near you. This mixes into the water and should help the issues.
Chicks that you help hatch are usually weaker than others. I would for now give her some electrolytes. Feed stores near you should have some packets. Mix it with her water.
I don't have the bag anymore, but I believe that it has 18% crude protein according to the website. I am using Purina Non-Medicated Start and Grow Feed Crumbles.
I have two three week old ducks and the internet is just full of things telling me what to feed them. They are hatchery ducks not wild and I have been feeding them un-medicated starter with brewers yeast. They are doing great and growing very fast. However, I have seen so many people saying that...