Every animal gorws at its own rate just like snakes. Not all 5 month old mice should be 20-25 grams. She was big from day one and has stayed big. Her mother who is 77grams is 11 months old.

She may be obese but she still produced 16 pinkies every 3 weeks on the dot when bred. once they drop below 10 babies per litter i retire them.

and i dont go by 3 months for mice at all. 6 weeks their sexually mature and ready for mating.