Both my girls weigh 2lb they are 6 months old..they do not look fat to me but i am unsure after reading girls should only be 1lb 5 :{
I've seen quite a few places that say a guinea pig should only be 1lb 5. In my opinion I find that a very dangerous weight to inform people. If my pigs were 1.5 lbs, they'd be quite underweight. I see the weight of 1.5-2 noted for boars too. They should be around the 2lb with anywhere up to 3 lbs also completely normal and not overweight. Boars tend to be a lot more muscular, so they weigh a hell of a lot more. I had one boy that was the same size as his mother that I owned. His mother weighed 1kilo, he on the other hand was 1.4 kilos - 3lbs of pure hunky guinea pig. I've seen bigger than him too!
I've got one girl that is only about 600g, but she is most definitely an anomaly; she is very small and quite thin, it's the way she's built I think (I've only had her a few weeks now, she's approximately 3 years old).
I've never had a girl under 800g otherwise, and my adult girls, aside from Bean, are all around the 1kilo mark now. I have one 10 week old girl who is getting pretty damn big already. She's bigger than the 14 week old I have, and much more well built than she is. I'd say she's going to be a 1kilo+pig.
At 6 months old, your girls will still be growing I would have thought. You're probably going to have 1kilo+pigs. It's perfectly normal.
NOTE: This is not to say that people with 1.5lb pigs have underweight pigs. Small pigs do occur (as do abnormally HUGE pigs) and they're no less healty than bigger pigs! But in my experience, I've had over 20 guinea pigs and met quite a few more, the average for a girl is more like 850-1200g (just under 2lbs to over 2 and a half). Males anywhere from 900g to 1600g is a normal range.