If 53% is the highest you can get it, then I wouldn't worry about it too much. Ideally, it should be a little higher, but they'll be fine. Especially after the first couple pop out and the humidity goes up on its own. Make sure you use really warm water when you drop more in. Sounds like you've got a full incubator...how many are you hatching? Auto turner or did you hand-turn?
Keep us posted. Good luck on your hatch!

