My chickens are about 7 or 8 months old and they love to play in the rain. I have never dried them off and they have not showed any ill effects so far.
Acutally when they were about 2 months old I had them in a large temporary (rigged) pen in the yard and only one 1/3 of it was sheltered by boards (on the top and sides) and we got a really bad storm. I worried and worried about them. Finally I donned rain gear and a flashlight and went to check on them. Every single one of them were as far away from the sheltered part as possible. All were huddled in one corner being rained on. I figured if they were not smart enough to get out of the rain then perhaps an early demise was in order. Just kidding i did figure though they had a choice between shelter and rain and if they were choosing to hang out in the rain then they would be fine. I havent worried about the rain since.
I hope your chickens did well recovering from their ordeal and that you did not have to worry to much. They are hardy birds I have come to find out.