I bet you are doing a great job. Both you and your DH should spend some one on one time with each of them. Plus plenty of family time too. Praise them when they do things right. Cuddle them a lot and don't forget the hugs and kisses!
What do they do for you to think they are not? Does one or the other act different when the other gets some thing from the store? My oldest is 12yr. and gets mad when the 6yr. old gets some thing. It can be from a family member giving them a gift. Not every time all the kids can have some thing at the same time when i have 4 kids.. If they are old enough just ask them.