Hi there! Try not to worry too much. It is actually completely normal for a mother cat to leave 2-week-old kittens for 6 to 7 hours at a time. Now that they are growing, she needs to hunt and eat more to keep her energy and milk supply up. The best and most affordable solution is to feed the mother, not the kittens. Place a bowl of cat food and fresh water near their nest. If she has food right there, she won't need to leave the kittens for such long stretches. If she completely abandons them (gone for 10-12+ hours and kittens are constantly crying), you will need Kitten Milk Replacer (KMR) or plain goat's milk. Please do not give them cow's milk, as it causes severe diarrhea.

Give kitten milk replacer in small amount if cat doesn't come

If the kittens are less than 1.month then give them milk replacer

U can give Kitten wet gravy, curd etc as initial food.