HELP,sick bird!is this a proper diet for house sparrows?? :(?

i found 2 baby house sparrows 2 months ago,i raised them with dog food and they were very healthy.But last week one of them suddenly died and the other is sick.He sleeps at the bottom of the cage,hia feathers look damp and are broken in places,and his tail seems chopped off.He sleeps a lot during the day and cant fly very high &doesnt talk anymore.I have been keeping them in a very big cage.I looked at his tail&i saw his uropygial gland,but cant determine if its ok.Its not red and its about the size of a pea.I ve called animal rescue,but in my country there are not many organisations like that.They said they didnt want him.Im so worried i could ve caused it by not feeding them right.Ever since they started eating on their own,i have been giving them seeds&veggies&some chicken,but they didnt eat the chicken or dog food i gave them.I give him vitamins and his diet now is a lot of things mashed in the blender(i found out he eats everything this way,instead of picking).This is what i put: 1 teaspoon of each:apple,apricot,lettuce,peas,chickpea… beans,rice,carrot,banana,tomato,corn,pot… boiled but the fruits),a few teaspoons of ground puppy pellets and 1 cup of grilled chicken & a few vitamin drops.I put it in the blender and he eats it like crazy.His droppings are normal.Am i doing the right thing?I dont want him to die too :'(