A third pellet meal?

Kenzo just got sheared today, and the animal stylist and I both agreed that he is VERY skinny. It's hard to tell when he has all that fur, but now that he is sheared we can see his ribs and he is very small.
He eats well, infact he eats alot, so I was wondering if I should give him a third pellet meal during the day.
Kenzo & Chewy eat pellets once in the morning and once in the evening, have daily veggies, and hay 24/7, so giving Kenzo extra pellets seems like the best thing to do for me...
Should I do that?
Are there other ways for him to get a bit fatter?

Some people use pre-soaked porridge oats (need to be soaked, else the expand in the stomach) for weight gain. How old is Kenzo now? You could (and I would wait for further advice on this) give him Alphalpha hay, which has a higher protein content, and is usually not recommended for adult buns because it is fattening & can put stress on the kidneys (can someone else clarify that or not?)

Just out of interest, what size is he and what breed, and what does he weigh?
Which pellets are feeding him? There may be a better one for him, as some have too much sugar and not enough fibre.
Sorry for all the questions, just need more info.

Buns should be on the slimmer side, although they can also be underweight too

As Jay has suggested there are other foods which can be given to 'fatten' bunnies up. It is also not unusual for some rabbits to lose weight over the winter ,months when they burn more energy keeping warm. For this reason I switch my rabbits to a higher protein pellet from October to March and this generally solves the problem.

You could try putting him on a richer pellet whilst he builds up, just remember to change between foods gradually to prevent a tummy upset. You could also offer pellets ad-lib if you will be sure he will still eat hay alongside this.

I notice you say that he eats well, so I wonder if you have actually been watching him eating yourself, and I also wondered if he and your other rabbit live together....

thanks alot for the replies!

Response to Jay:
Kenzo is 1 year and 3 months old.
I don't know how much he weigh since I havn't checked in a while, I will weigh him as soon as I have the time (probably today).
He is an american fuzzy lop/angora mix (the big white angora ones).
I feed him (and Chewy) Alphalpha pellets for rabbits, if you want I could write the composition here?
I will compare these pellets with others next time I go to the pet store, to see if they sell ones with more fibre/protein.

response to Sooz: I will try to find better pellets. I always watch my bunnies eat their pellets (that's a reflex from when I had a horse, I always observe my pets eat )
And when I'm home during the day (which is often) I always spend time with them and Kenzo does eat alot, usualy even more than Chewy.
My bunnies do live together.

That's OK, I just asked as sometimes rabbits can miss out on their fair share if they live with a partner who is a faster eater. If he loses more weight or develops any other symptoms it may be worth a vet check up, as weight loss can be a symptom of several medical conditions, the most common being dental related problems.