Hi lemon,
Unfortunately what you think is very good food for your rabbit actually is not. Corn, nuts, seeds, dried fruit and veggies are not good for your rabbit. First off they do make a rabbit gain weight rapidly, things that are high in starch like corn, seeds and nuts (peanuts are actually a legume) can cause an impaction in your rabbit (GI stasis) and and sugar (molasses) is very unhelathy and unbalances the the friendly flora in the gut and also makes them gain weight. A rabbit who is on this food it is often hard to give regular pellets as I liken the stuff that you are giving your rabbit to fast food and junk food.
It is important to remember that even though something is sold in a pet store for rabbits, does not necessarily mean that it is good for them. Major pet store brands often cater to what the owner of that animal will like and not what is actually best for the animal.
I first recommend you switch slowly over to a “plain” good quality rabbit pellet that does not have alfalfa or any other junk in it. Mix 1/4 new with 3/4 old for one week, then 1/2 new with 1/2 old for one week, then switch completely over to the new pellet. You will want to try and pick the colorful bits and whatnot out of the old food when you do this as the rabbit tends to go for the not-so-good junk food like nuts, seeds, sweet stuff. Here are some guidlines for feeding your rabbit: https://binkybunny.com/Default.aspx?tabid=60
Are you feeding him any hay at all? The majority of the rabbit diet should be timothy hay. Also, is your rabbit altered at all and how long have you had your rabbit? Are you sure the rabbit is male and maybe not female who is about to have babies?
Some good web sites to look at (of course here too!):
http://www.rabbithaven.org/index.htm
http://www.rabbit.org
http://www.rabbitnetwork.org/
http://www.saveabunny.com/
There are many other rabbit rescue organizations depending on where you live that will provide information as well. 