1. My 5 years daughter lost two teeth forcefully and it has refused to grow, will it grow later?
2. My twin, 1st was born 2.2 and now weigh 4.3, the 2nd was born 1.8 and now weigh 3.5 they are 6week
To your second question- Please read this on child's ideal weight. WHAT IS MY BABY'S IDEAL WEIGHT?

AT BIRTH.....the BIRTH WEIGHT normally ranges from 2.5kg to 4.0kg
Any weight below 2.5 is LOW BIRTH WEIGHT
Any weight above 4.0kg is LARGE FOR AGE BIRTH WEIGHT or MACROSOMIC or BIG baby
After birth, Babies FIRST LOSE WEIGHT in the first 10 days.....before regaining their birth weight by14 days......
So it is not unusual for babies to lose weight first... Don't panic.....This is as a result of losing fluids, inadequate feeds at the beginning, and so on....but as the feeding become established they regain their birth weight at 2 weeks
Babies gain weight thereafter usually about 30g per day for term babies; 20g per day for preterm babies
That is roughly about 1kg per month for term babies and 600g per month for preterm babies
At this rate...Children DOUBLE their birth weights at 5 -6 months and TRIPLE their birth weights at 1 year
Remember we are talking AVERAGELY.......Some babies do gain a little more; others a little less......So You don't have to worry as long as your baby's weight falls into the 80% - 120% range of the average weight I mention; it is OKAY!!!
So let us do a little maths......Average weight at birth is 3.5 kg.......at 5 months, doubling will mean weight of 7kg and triple of weight at 1 year will mean weight of 10kg
It could take up to 1 year or more for the adult replacement to come in