Babies often prefer the sweet foods. Baby milk is very sweet, and it takes time for them to develop the taste for savory. Could you mix foods. I used to keep a tray of steamed and pureed apple in an icecube dish in the freezer, and add one or 2 to pureed veggies. My ds used to prefer the jars of veg, but was ok with me pureeing fruits.
don't worry, its normal at this age, and also echo what the others said, that you musnt worry, if he's getting a good balance of milk and solids he will get the calories he needs
but i do understand, my ds didn't grow very quickly, and it was a struggle and worrying time. Big hugs