You can even try supplementing with porridge or rice pudding with puppy milk too.
We worry so much about our tiny Ice (29g) but to be honest, whatever we do she seems to stay the same, she doesn't seem unhealthy, is active and happy! We didn't realise how small she was until we went to hamster shows and saw some of the dwarf show hamsters (which were over twice the size of her!!) pet shop hamsters tend to be smaller.
She is just a slim girl, maybe Mishka is just the same.