My Conure refuses to eat! help!! :/?

Hello, my conure which is around 11 months old! i got him like a week ago from a previous owner .the problem is he is hungry and i can see him beg for food yet he refuses to eat everything!! i gave him pellets, mix seeds, sun flower seeds, veggies and fruits! he doesn't touch anything but he does force him self to eat some sunflower seeds!! but for a small portion! so he does not eat and he drinks a lot of water which i think its the reason behind little amounts of small droppings (little of separated feces, Lots of urine mixed with the urates)...i cant contact his previous owner so that i could ask him what his diet was!! ... so Please help!! what should i do!?