Just a question from a very over-cautious first time mum...

I just had a check-up and had my DS weighed and measured. He's always had really good gains, the smallest being 340g over two weeks. But today he had only gained 140g over two weeks. He had also grown 2cm in that time though, so maybe he'd been doing more growing than weight gain??? Is it normal for weight gain to slow like this about now? I just know I'm going to obsess and worry about this if I don't find out .