Problems with changing cat food-help!?

I just started to learn about all the gross things they put in pet food so I switched my cat's food. He was eating The Goodlife Recipe (which he LOVES- and which I can get for not very much money at walmart...) to Natural balance soft food (1 little can twice daily) and supplement that with Wellness brand... show more I just started to learn about all the gross things they put in pet food so I switched my cat's food. He was eating The Goodlife Recipe (which he LOVES- and which I can get for not very much money at walmart...) to Natural balance soft food (1 little can twice daily) and supplement that with Wellness brand indoor hard food. Since switching he has had black stools and only a small one every 2 days or so, when he used to go every day regularly & they looked very healthy. He doesn't like his new food very much and always scratches at the floor to try to "cover up the smell" is what I'm guessing...like he would in the litter box. He hasn't been vomiting as much as when he was on the old food (although i think they were mostly hair balls), but still does occasionally and its clear with loose hairs in it. He also seems to be sensitive about the area near his hips and it feels like his kidneys might be a little swollen, but I haven't taken him to the vet about this yet. No notice of increased urine output or thirst & no real changes in his behavior besides in relation to his food. Should I just switch him back to the old food or stick it out? It seems like the "healthy" stuff might be causing more problems than his old food! He has been eating this new food for about 2 months now and he will eat it but he always does the scratching thing...some flavors more than others. I would appreciate any help or adivce! Thanks
-Grace
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