My son also had low sodium levels and high renin results in infancy and I was told that this was the reason his growth was so poor in his first 2 years - he was off the centile charts (he weighed 8lbs 2oz at birth and only 14lbs 1oz at 12 months).  I was surprised, I hadn’t realised that salt helps with growth!  I am sure your daughter will catch up though and the growth is only delayed, as although my son remained one of the smallest in his class through childhood, as he went through puberty he started to shoot up and at 16 is already almost as tall as his father and he is still growing!