How are you washing them? (how much detergent, water temp, type of machine, etc) How long is your kiddo in them for? What covers are you using? The more info you give, the more we can help you try and figure this out.
I put them on a pre-rinse in our top loader washing machine, then put them through a full wash with 1/4 cup of detergent (this is what I use with all my clothes) mostly I wash on cold with the odd cycle on hot. I am using the pul covers

In regard to how long ds is in them tonight he was in one for 1/2 an hour when he was wet completely through