Just seeing this now. The pictures are of recently emerged, new young bees. The white squiggly strings are remnants of her cocoon and pupa umbilical to the jelly pot at the base of the cell. It is normal to see on new bees that just crawled out of the cell.
The remnants get cleaned off fairly quickly by the older main nurse bees of the nest.
Bees dying before hatching have different causes. Varroa for one, EFB is the other, malnutrition (starved pupa), chill, excess heat; are the mains. Only you can know which it is.
Fecal matter of nurse bees is cleaned up and hauled out by the older bees. Like changing diapers. If there are not enough older bees for the tasks, you get what you see with squirts in the pictures. Fecal matter on combs is typically a result of a colony population in a house that is way too big for what they can look after. The colony is too small for the bees to go far to vent themselves without sacrificing brood cluster temperature. The bees go off a bit vent, and come right back to maintain the brood. Nosema is possible, but not likely the culprit when the population is too small to begin with. The example is when you put the dog out on very cold winter days. He does not go far does he? If you have a puppy or a small toy dog, she is likely not to go out all and would prefer to do her thing on the entrance rug right by the door, inside, without telling you about it.
Basically what I read and see here in the pictures is a colony that is too small for the space they are in, and a lack of age balance in the bees there to have the jobs covered. The queen performance mentioned is a symptom of the problem. Ie she is totally fine. Just get her a larger workforce to support her.
The fix for the condition described is to significantly reduce space, really greatly compact the hive. Crowd the bees. Test and treat for varroa if required. Check and treat for EFB if required. Boost with some older bees. Feed.
Hope that helps.
