I was staying with my aunt and uncle, who are vegan, for about 3-4 weeks. Everything was super-healthy, so I was really chowing down! Especially frozen banana "ice cream" made in the champion. And, I was so gaining weight. I eat a predominantly vegan diet, save the occasional beef, chicken, or fish indulgence (maybe 2-3 times a week). But normally I eat much more balanced, in terms of fruits and starches, compared to veggies. But wow I sure was gaining while staying with my aunt!
Fruit and LOTS of rice, and bread, all those things can make you gain weight! If I were you I'd cut back some on those and make sure you're getting loads more actual vegetables. Be careful with dried fruits and nuts, as well.

Of course there can be other explainations, as well. I'll be interested in what others have to say.