Congrat's on your new baby first!
We all had our doubts about cloth nappies at the beginning, so don't worry.
My DS was about 8-10 weeks when we first started with him.
What do the marks look like on your little one?
Sometimes mine get 'inprint' type marks, from the fabric being next to skin - that's fine.
Or are you talking about sore patches??
When it comes to night time and now that she sleeps for longer - as long as you have a nappy that is boosted enough that it doesn't leak, then don't worry. I know its easy for me to say here - but its fine to leave it on for longer as long as it doens't leak & there is enough absorbancy to see you through.
Just play around with the absorbancy.
My DD is roughly around the same size as your little girl (she's petite for 4 months)
It's taken us a week or so to get her night nappy right. She doesn't wake us unless she wants a feed.
So if she was damp in the morning from leaking (she's a heavy widdler too) - the next night we added an extra booster, until we got it right.
You don't have to switch 100% all at once. Just start using your cloth gradually.
As you grow in confidence at using them & know what suits your little girl - you'll use them more & more.
There are loads of us on here - who've had the same thoughts
So any questions, just ask!