Im may opinion, changing from one food from another, merely because the dog wont eat, creates more problems than it solves.

Wainwrights is very similar to JWB, so isnt a bad one to be on. How many meals a day is your dog on?

Id be inclined to try time controlled feeding. Place the food down for a set amount of time, say 20 mins, and leave it there. After the 20 mins anything that isnt eaten, is picked up and nothing else offered until the next meal. You dog will soon realise that it either eats whats offered or goes hungry. Mixing things and chopping and changing often creates a very fussy dog, as they realise that refusal gets them something new and tastier.

A dog wont starve itself, so dont worry about that.

Oscar was a fussy dog until he was about 7 months. If he didnt eat, he just went without. He now eats anything i put infront of him. I think its a phase many pups go through.