Humm, that’s weird. What kind of leaking is it? Overflowing? Compression? Wicking? What insert are you using? The bamboo ones are the most absorbent?

It could be the increased movement or just bigger wees as you have suggested.

Is your DD drinking more in this hot weather?

Have you tried boosting with a bamboo booster? The GK bamboo boosters are great IMO.

HTH, if not, come into the cloth nappies thread in the cloth nappy general discussion, the ladies in there are nappy super heros (they wear red satin capes with the letter “N” on the back).