With still the temp needs to be around 101-102.I have 2 Little Giant, still air, incubators. Both were set to 100 degrees with humidity at 55%. We candeled every 3 days or so, because the first batch was a complete failure, as I said. The hatcher is a converted fish tank with a heat lamp, wet hay, and a butter container of water. None hatched on time and we were so in experienced tha we kept them for 1 extra week because they were still moving in their eggs. 4 pipped but she was the only one that hatched. She as splay legged and wasn't eating. We tried feeding her sugar water and she would drink it, but still died 4 days later.
a we have now added a usb fan, an aluminum partition, and a mason jar of water for humidity, so we have better contol over the humidity and temp dispersment.
are the eggs on the Wet hay? the spraddled Leg one, did she get any niacin? Ducks needs naicin, as well as chickens. did you try to tie up her legs to help correct the leg issue? If she couldn't stand it would explain the early death. They have to hold there heads up really high and swallow, with her leg issue I wonder if she was unable to swallow properly.
Now that you have a fan your temp should be around 99-100, i would try to keep that humidity down a little more, more like 50 unless you are spraying/misting them, then I would decrease it even more.
To stable the humidity a little more put paper towels in the jar, then it wont evaporate so quickly..