I had the same problem with my boy. He is a very finicky eater and was just so thin and lanky looking.
He litterally would not eat...it was a nightmare.
Someone on here recomended a product called Dyne which worked really well--its literally a sugar type suppliment that is given to all types of animals to help fatten them up. I had to use this daily for almost a month to put weight on him.
When I switched his food to Natural Balance Duck & Potato (small bites) for the first time in his life he actually wanted to eat. I mix his food with the grated Natural Balance Lamb roll and a suppliment called K9 Show Stopper for his coat and he is SOLID now. I am very pleased with the resutls.
I would probably stay away from Evo as I have heard that too high of protien causes kidney issues in toy breeds.
Best of luck!