Call duck eggs not losing enough weight compared to others

[JuliannaM06]

Hello, I am incubating 10 call duck eggs at the moment. It is day 17 and 6 eggs are on track with weight loss, within .50-.75 of a gram. I have two eggs in the same incubator at 50-55% humidity that are barely losing weight, around .10 of a gram per day. The air sacs are significantly smaller, only a bit bigger from when they were first placed in. How do I help them along without effecting the others? I already am using my second incubator to aid two other eggs that are losing weight incredibly fast, even at 75% humidity.