i have a litter of pups (toy breed)which are 6 weeks old now.i have had to syringe feed 2 of them from 2 weeks old as they were losing weight very fast, but thankfully i have persevered and after many long sleepless nights they have come along great. They are still half the size of their other 3 sisters but they  are the first ones to the food bowl and last ones away. i am wondering if theres anything i can give as a supplement to help them fill out.  they are gaining weight daily and are playing with their siblings and are doing what the others doing, Should i just keep feeding them the solids but more often than the 3 bigger pups or supplement them if possible

I only ever had one litter of pups and they were Barf fed from 3 weeks. They had raw minced chicken/lamb/rabbit with raw vegetables mushed in the food processor. I always gave them a small bowl of goats milk after each feed and would put a raw egg yolk in it for their supper. As mine were weaned on this diet they gained weight quickly and, like most barf fed dogs/pups, had no tummy probs at all.
Have always fed Barf even to my chihuahua cross and my yorkie cross, raw chicken wings/bones/carcasses/necks everything raw. My three Malamutes have Barf and I originally changed to it when my first Mal had terrible tummy probs as a pup.
My pups were real lil chunksters!
What are you feeding your dogs?

I second raw mince, it's what I've reared my toy pups on to start with, then add Nature Diet and other things. Mince really seems to put the weight on.

hi im feding them soaked royal canin and tinned puppy food and also giving them goats milk.  i will try the chicken and see how they get on. thank you

Just a warning note: are you aware that dogs can contract Neospora from raw mince? The simple way to prevent this (it is potentially fatal) is to freeze the mince for 24 hours, then thaw & feed. Cooking kills the Neospora too. The more we learn; the more we worry!

Pet mince is always sold frozen. :) I wouldn't feed mince for human consumption as it does not have the bones ground into it. Far more expensive too. :)