Hi everyone. I have a friend who had a cat have a litter of 8 kittens. They turned 4 weeks old yesterday and 1 is significantly skinnier than the others and less playful. I told her she may want to supplement it a little with some replacement milk. She was wondering if she can use baby formula until she buys some? I've hand fed plenty of kittens, but have never used baby formula so I wasn't sure. Any advice is greatly appreciated.