I'd say the "clear sheath" is bacterial growth. I've had lotus fail like that before. I don't know how to treat it: maybe a little hydrogen peroxide. I hope you figured something out in the two weeks since you posted this question. I don't think adding the liquid fertilizer helped, but I could be wrong. I'm sorry no one with lotus expertise chimed in.

I did remove it a bit but i think I am still just a beginner here with Lotuses. Where they are gets sun a few hours a day and algae is insane. I put one in my pond and the fish attacked the little pads. Do most people do this in a greenhouse? or just a pond? I have a few growing indoors at the moment and i don't see that clear surround. I did see it initially when the seed opened but that was it.