Don’t confuse a differing parenting style with neglect.
What is your evidence for thinking your ex is not looking after the children?
Are the children happy, clean, fed?
Are they worried or stressed? Are they worried because you’re worried?
Remember: if you have been the main carer and the non-resident parent has been only semi hands-on during your relationship, there will be a certain amount of ‘learning’ taking place. That doesn’t mean there is neglect.