Breastfeeding question

Ok so my daughter feeding have decreased in length. She eats between 5 - 7 minutes of the first breast and less off the second. The first breast feels lighter afterwards and she has a wet diaper every feeding. She used to poop every feeding now its about every other feeding. I weighed her in Monday she was 7 lbs and 7oz. She was 7 lbs and 4oz at the last dr visit so she has gained a little. Should I be concerned about the amount of time she nurses or is it ok so long as she has wet diapers and is happy between feedings and has had some weight gain?