Very picky Himmie kitten

I have a nearly 8 month old Himalayan kitten who's very picky about food. He'll eat a new food for a day or two and then decide he didn't like it. He just ate a dried apple chip while ignoring his dinner. I've tried 4Health Grain Free, Purina Kitten Chow, Purina Beyond Salmon and now Science Diet Kitten. He seems to like fish flavors over chicken. The only thing he'll consistently eat are the Friskies mixed treats. I have 5 other cats and 2 dogs and everyone is schedule fed, so I can't leave his food out or someone else will eat it. Does anyone have an economical food choice that I can try? How did you stop your cat from being picky? I've never had this problem before.

Here's the little punk after eating his apple chip and about a third of his actual dinner.

Some cats are just naturally picky, I think.  I have two cats that are one day apart in age.  They grew up just the same.  One will eat pretty much any and everything I give him.  The other will eat two things and two things only.  Nutro Natural Choice Chunky Chicken (no other flavor), and Fancy Feast Turkey and Giblet CLASSICS.  I finally found a difference Turkey and Giblets wet food, and the ingredients are almost the same, and he will not come near it, AND if I mix even 1/8th of a teaspoon of the new food into his Fancy Feast, he refuses to eat at all So...I feel for you, being right there with you.  Once I got so desperate I tried kibble since a sample came in with the litter.  I had no idea what it was and wouldn't even attempt to eat it.  (just as well)

At 8 months you should be able to move him off kitten food and at least start looking at All Stages foods (there are tons out there) if not Adult Food.   Since you have 5 other cats who aren't picky, it's not like you'll be wasting your money if he doesn't like what you buy.  Just keep trying different foods, different flavors, different styles...pates, chunks, slices.  And he may simply be the type of cat who likes a variety.  Try giving him chicken pate for breakfast, tuna chunks (cat food) for lunch, and lamb slices for dinner, then the next day something totally different still.  That's what I do with my OTHER cat so that he doesn't become pickky.  I feed him a variety of brands, flavors and styles.   

And you can always use the Friskies Mixed Treats as toppers for his wet food.  Crush them and sprinkle them on top.

They get dry kibble most of the time. I can't afford to feed 6 cats wet food for every meal. They get canned foods for lunch every other day. Even with can food I have to put treats on top. He usually eats the treats and leaves the rest.