increased amniotic fluid

Hey everyone. I am 31 weeks and 4 days with boy/girl twins. I have routinely seen my OB doctor and a high risk doctor through out my pregnancy. Today I went in for my ultrasound and they said that my son had a little bit more amniotic fluid then he should but that my baby girl had the normal amount. The doctor gave me no real explanation to why he had more fluid at this visit vs prior visits. She said he is measuring proportional to his body and I also passed my glucose tolerance test weeks ago. I go back next week to re check his fluid level. I left thinking nothing of it. Well then I got on google...... and everyone was saying how increased fluid can be a sign of Down syndrome, heart defects, or a lung abnormality. So now I'm freaking a little more than I should be. I opted out of the AFP in the beginning as I was told with multiples it's never really 100% accurate. What is everyone's thoughts? Has anyone else had this happen? My doctor said that this normally corrects itself and no worries and that the baby looked wonderful. By the way today they were weighing boy- 4lbs 8oz and girl- 3lbs 15oz! Which their both measuring two weeks bigger than what they are. Can anyone else share their experiences with me on this?