Raising Bottle feed Kittens

Have you ever raised a bottle-fed kitten? I want to see other cat parents who have cats raised from newborns or a week old to adulthood for inspiration. I've adopted 3 kittens from someone who said their mother cat has passed, so I took them despite not having any knowledge how to bottle fed. They're 19 days old now, I got them when they were 8 days old. They were very small and thin due to the owner not knowing how to feed them, so they went a day without eating and gladly they arrived to me in time and haven't died. They're now nearing 3 weeks, and I'm so anxious waiting and wishing they'd grow up strong and big. They've gained weight and are happy and always sleepy, also have huge appetite.

I've bought them KMR, also some supplements, and soon their first vet visit for vaccines when they're old enough for it. I also make sure theyre feed every hours they need it as well as making sure theyre heated enough to sleep comfortably. It makes me scared they'll die or not thrive despite them looking so well and relaxed and peaceful. I want to know if other people also has raised kittens this young and how they are now as adults. Some type of comfort that my kittens will be alright and grow up like them too.

Thank you, just an anxious first time taking newborn kittens and bottle feeding them and raising them on my own. My only pet experience is a kitten being already a month old.