Peeing through overnight diapers

Hi, for the last 3 nights my baby has been peeing through her overnight diapers. She wears a size 3 Huggies. We just sized up from a 3 so I know that’s not the issue. She goes to bed at 8 pm and by 1 am she’s soaked through. Any ideas why this is suddenly happening? She used to sleep 10 hours without peeing through. I thought maybe she was cold but our room is set to 70-71 and she wears a sleeper underneath a Merlin sleep suit.