For growing bunnies like yours, alfalfa is fine. So you could give alfalfa based pellets and timothy hay. You can give alfalfa hay too but skip this is you find his diet it too rich. Rabbit mixes are really not ideal. A plain pellet with around 14-16 % protein and over 20% fiber is better. You may find alfalfa based pellets are around 18% (ok for young bunnies)

This is House Rabbit Society diet recommendations:

What quantities of food should I feed babies and “teenagers”?
Birth to 3 weeks–mother’s milk
3 to 4 weeks–mother’s milk, nibbles of alfalfa and pellets
4 to 7 weeks–mother’s milk, access to alfalfa and pellets
7 weeks to 7 months–unlimited pellets, unlimited hay (plus see 12 weeks below)
12 weeks–introduce vegetables (one at a time, quantities under 1/2 oz.)
What quantities of food should I feed young adults? (7 months to 1 year)
introduce timothy hay, grass hay, and oat hays, decrease alfalfa
decrease pellets to 1/2 cup per 6 lbs. body weight
increase daily vegetables gradually
fruit daily ration no more than 1 oz. to 2 oz. per 6 lbs. body weight (because of calories)
What quantities of food should I feed mature adults? (1 to 5 years)
Unlimited timothy, grass hay, oat hay, straw
1/4 to 1/2 cup pellets per 6 lbs. body weight (depending on metabolism and/or proportionate to veggies)
Minimum 2 cups chopped vegetables per 6 lbs. body weight
fruit daily ration no more than 2 oz. (2 TBL) per 6 lbs. body weight.

http://www.rabbit.org/faq/sections/diet.html#basics

Keep treats to very small amounts. The sugar can cause a gut imbalance. You mentioned him not eating all his cecal pellets in another thread. This may be because his diet is a bit too rich. This is when they produce excess amount of cecals. Also, extra vitamins in the water is really not necessary. Their diet and cecals should provide all they need.

A belated Welcome by the way!

Don’t give them seeds or nuts, or corn of any type, they cant digest them, and some can even be harmful for them. Its better to stick with plain pellets, hay and eventually a variety of veggies once he is old enough.

By the way, any changes you make to his diet – do so slowly. Sudden changes can cause a gut upset. So it’s best to wean them off one feed and gradually add in the new. Does he eat the pellet portion of the Vita bits? If he does, you could pick out all the other stuff and give him the pellets, then gradually transition him onto a good quality plain pelllet. You can have them on pellet – free diets but I’m unsure if this is wise for a young growing bunny.

It can be very confusing with the amount of conflicting information that is about.  Rabbits are raised / kept for different purposes and so there is varying husbandry info offered.  This site provides info based on the House Rabbit Society guidelines.  Specific to house rabbits.  The HRS info comes from a lot of well informed, experienced people that know rabbits as pets. Owners, rescuers and veterinarians that have seen many, many rabbits!  I have also seen that the HRS info is widely quoted and recommended. So for me, I stick to this school of thought to guide me.

This is a great article from a well-known and respected rabbit expert, Dana Krempels… http://www.bio.miami.edu/hare/diet.html

She explains every part of the diet very well. Jersey hit the nail on the head when she said that “rabbits are raised/kept for different purposes.” Breeders and those who “use” rabbits don’t necessarily care if they live past 3 or 4 years. As long as they get what they need out of them, they’re satisfied. Us as house rabbit people, we want our companions to live as long as possible. This is why we feed our buns as close to what a “natural” diet would consist of. We recognize that babies need more protein and calcium to help them grow, but it’s not necessary as they reach maturity.

I agree that there is a lot of conflicting info out there in internet-land… It’s important to also have a good relationship with a rabbit-savvy vet. They will be a good resource for you for answering questions.

My buns get the Oxbow Bunny Basics T (for timothy) pellet. They share about 1/4 a day between the two of them. And for the past 6 months or so, it hasn’t been uncommon for them to not finish all those pellets. They really do prefer veggies and hay over pellets. Since your bun is a large breed, he’s going to need that added nutrition right now, and he will grow quickly (so take lots of pics!)

My bun Lemony is about 5 months old, and ever since we got him we have been giving him unlimited Oxbow alfalfa and and unlimited pellets – we give him alfalfa-based pellets, because that was what are doctor recommended while he is still a lil one. We use Oxbow Bunny Basics 15/23, which is especially for juvenile rabbits. If he is eating more pellets than you think is necessary, perhaps add a little bit of alfalfa hay into the Timothy mix. Buns love that stuff. Lemony will eat a lot more of the alfalfa hay than the timothy hay if offered both.

But yes, I am pretty sure that they are supposed to grow that quickly. I think it’s a good sign that he has a healthy appetite! Just watch for he fecals – they give the best indication of his overall health. Lemony has grown exponentially since we have had him. His is up to 4 lbs (we got him at 2 lbs) and his still supposed to double in size. So it sounds pretty normal to me!

Also, as jerseygirl said, any changes should be done gradually… The rule of thumb in our house is that if his fecals look normal, than we can go forward with any changes step by step.

Btw, you bun is adorable.  I love his ears!