I am going to be of little help here. You have the experts on board now and I can't offer anything more. I was going to suggest the yogurt and I do remember Craftlady saying the the pumpkin really helped do the trick. She had a horrible time with Skinny as I remember.
Thank goodness they like the yogurt so you don't have to force it on them. Hopefully when you mix the pumpkin with the yogurt and they will eat it. It is really supposed to help bind the poo. Hopefully the good bacteria in the yogurt will take over and kill all those nasty bugs!
I wish I had more to offer but all I can give you is my support. I'm sorry you are having to go through all of this. I know how much you love the babies and are doing everything possible to make this go away.
Prayers, good thoughts, and my sympathy are with you! If there is anything I can do just let me know and be sure to give kissies to the sweeties for me. Poor little things!