Try loosening the belt clips and see if that helps any - that's what I had to do. Sometimes the vests don't quite fit right and you have to adjust them. Like I am sort of in between vest sizes, so I opted for the smaller one and just keep the belts really loose. But if she hasn't grown at all it could be the pressure setting or just the way it's fitting her chest. Talk with your RT or RN if it continues to be a problem, they may have to change the vest size.