oh my..what happened to cute and cuddly?

My kittens are growing so fast. Seriously, I leave in the AM and come home from work and wonder what happened to them.
Tundra is now almost 24 inches long when laying down from tip of nose to bottom. I just measured his tail at 11 inches long. Is this normal?
The vet did say that they were both going to be big cats.
They are still only eating 1.5 oz of canned + 1/4 cup of dry Authority kitten in the AM and and again at PM. Later on at night they share a 3 oz pouch of Nutro only. That is still under what the recommended feeding is.
I do leave out Authority dry during the day a heaped 1/4 cup scoop which is sometimes gone, sometimes not when I get home.
Should I go to wet/canned only for a while?
Could it be that they are older than the vet thought originally?

So glad they are growing and doing well. If they are healthy according to the vet and seem satisfied after eating, they are getting enough. You can check the label on the food that lists the suggested amount to feed. It is only a guide. Looks like you are doing a great job.