They are fine now. Still pretty low on percentiles even at 7 yr old but thats just them naturally, they eat like horses and are always on the go! My girl (the one born on 6th percentile) was initially OK with weight gain but after at 6 months she stalled and started loosing weight even thou she was eating well and no illness. I had to put her on a high calorie diet for a few years to keep her weight gain up. Both had a stall in growth and stopped gaining weight completely between 12-16 months old. Now they are 126 cm and 125 cm tall and weigh 22KG.
During the 3rd tri I was scanned twice a week to check cord flow and liquor levels, measurements taken once a fortnight. Between 20-28 weeks I was scanned around about once a fortnight. I am not sure if your little ones are sharing a placenta or not, but if they are, I assume they are keeping an eye on you for TTTS too?