Hatching silkie problem

[TOR]

I have been hatching mixed large fowl and small bantam eggs together, Silkie. The large eggs I get 80 to 90 percent hatch rate. The bantams maybe 20 percent. The bantams look good at lockdown. Hatch rate sucks. My second hatch I had 2 silkies with splayed legs and a 3rd with bit wry neck and splayed legs and all those 3 ended up dying. The silkies eat the same food as my large fowl birds since I get a good hatch rate with large eggs I am thinking it is not a nutrient deficiency. Anyone else hatch mixed large and small have this problem.
I use the old styrofoam incubators with force fan, heat. The one styrofoam I do get some temp fluctuation. I suppose degree and half, I use a STC 1000 with it. I am getting to think it is a temperature problem.
Thanks

 

[Yardmom]

Do you keep the eggs in the same position each time? I have hatched both together with similar hatch rates, but I have not done it enough to watch for trends. Have you let broodies hatch the Silkie eggs to see how they do?

 

[TOR]

Do you keep the eggs in the same position each time? I have hatched both together with similar hatch rates, but I have not done it enough to watch for trends. Have you let broodies hatch the Silkie eggs to see how they do?

I do have any broody silkies as of yet. The second time and third time I did some rotation of the eggs. I am incubating again and going to switch the eggs around more this time. One incubator is a little giant and I use the controller with it. The other is a Farm innovator. I was thinking maybe the temp difference from the big eggs to the little eggs in the turning trays.
I am gonna try to hatch just silkie eggs next. Maybe I can figure this any ideas would be helpful though