How old are they? i agree you cannot keep flip flopping them, they build resistant if allowed too, it would be like be dressing you in your warmest stuff and tossing you in & out of heated buildings you;ll want to remove layers.
Key things, is not drafty buildings, well vented and good bedding and finally ensuring there well fed. If these birds are already laying there should be no question where they are, outside, only young non feathered birds do you have to be mindful with.
It's not i am heartless i do get it, but if they aren't allowed to gradually build up to the temps there will be problems, my daughter has some silkie chicks in their coop and they are young, pushing into the 8wk mark, no heat nothing special, they were kept in the house for 2wks while feathering out(she only got them at 4/5wks off heat lamp from the breeder)
I have ducks as young as 4mths here, Scovies and some calls.. they all live outdoors, i'll even top that and say i had a nest this past March from a determined scovie! yep, March!