How to make air cells bigger?

[AMoffat123]

I have just candled my duck eggs at 21 days and the air cells seem really small, I have turned humidity down to 20%, is there anything else I can do?

 

[AmyLynn2374]

I have just candled my duck eggs at 21 days and the air cells seem really small, I have turned humidity down to 20%, is there anything else I can do?

Not really, it's all dependent on humidity.