Oh no, Susanne, I do not do it for the chickens. Ducks need higher humidity to hatch well, supposedly. They have much thicker shells and membranes and the female ducks go swimming and then come back in to sit on eggs while still damp so that helps them but chickens are drier and on the last few days before a duckling hatches you can really hear it in the shell working to get going. I worry I will have it too dry and they can't hatch so I place a warm damp cloth on the nest then put the eggs down and then the hen can sit on them. Seems to work well to have them hatch.
You are good with yours unless Guineas need higher humidity but I doubt it.