If baby is active playful then no need to worry Baby gain weight 200 gms per week for first 3months of age Baby doubles of it's birth weight  at 5.5 months of age and triple at 1yrs of age. At 1yr weight should be 9-11 kg At 2yr 10-12 kg And at 3 yrs 12-13 kg Height baby gain height 4cms per months for first 3months and thereafter 2 cms per months till 6months of age. Baby may achieve height 73 -76 cms at 1yrs of age and 85-88 cms at 2yrs of age. 

It is normal. Your child is between -1 to -2 z score as per WHO growth chart. Weight at this age also depends on birth weight and length. You yourself can see your babies growth and plot it on chart. http://www.who.int/childgrowth/standards/chts_boys_z.pdf?ua=1