There are a few possible reasons why your baby is waking up earlier than usual.
Habit
If your instinct is to get bub up as soon as they make a little noise in the morning, likely they may be getting used to this and so will begin to expect it.
This can be addressed with sleep training, take a look at our favourite list of Baby Sleep Consultants.
Environment
External factors could influence when bub is waking up, here are a few things to keep an eye out for:
Light - Try to eliminate light in the room, making it as dark as practically possible turning off all sources off light in the room and using blockout blinds. If blinds aren't an option, adhesive films can be used to block out light.
Noise - Depending on your surroundings this can be a hard one to control, so sleep aids like white noise machines can help to minimise disturbance of background noise by introducing a constant level of noise to the room.
Temperature - Ideally we want to be able to dress bub once for the whole night, not waking them constantly to check if they are hot/cold. Generally the advice is to dress bub not for the current room temperature but for the 3-4 AM room temperature, but this can be hard to predict. If you're ready to take the guesswork out of dressing bub for sleep be sure to check out the Sleep Like Goldilocks sleepwear guide which predicts the overnight room temperature and suggests the ideal sleepwear combo for the whole night.