malnutrition

So i have 6 day old baby rabbits, 5 of them, but one is much smaller than the others,i gave him a millilitre of goat milk yesterday which is around 0.03 oz i think,and i gave him another today. He looks like what people refer to as a peanut,but niether of his parents are dwarves. Any suggestions...

I saw a feral rabbit for a few times and noticed that its black fur is turning into light grey and whitish color. Its back is also beginning to lose some of its fur. Is this a sign of malnutrition or a disease? How do we treat this condition? It hurts to see this bunny suffering...Please help...