The standard is that a hen will release one yolk to start the formation of an egg. It takes around 25 hours from the time that yolk is released until the egg is laid, on average. That is an average, some are faster, some slower. Some chickens ay lay 2 or 3 eggs a week, some 5 or 6, maybe occasionally 7 per week.
Sometimes a hen makes a mistake and releases 2 or 3 yolks at a time to start making eggs. I read somewhere that the record is seven yolks in one day. If the yolks are released at the same time you often get a double yolked (or more) egg. If they are spread out a bit you get separate eggs.
Most hens make enough shell material to cover one egg a day. With living animals you can get exceptions but it is pretty common for the second egg laid that day to be thin-shelled. Were all 25 of those eggs normal shelled? They may not have enough pigment to color both eggs either. Did all of the eggs look a normal color and shade? A hen grows the yolks inside her to a certain size before they are released. When I butcher my hens I can see the different sized yolks getting ready. If you opened those eggs were the yolks all the same size? What was their laying history before this past week?
25 eggs from 3 hens in 7 days does not sound right. My first thought is that another hen (or animal) is laying eggs in there. Is that possible? Another thought is that someone is pulling a practical joke on you.
