It's hard to say when you probably want to keep it grain free... and not go expensive. TOTW is the cheapest you're going to get, but you say it doesn't work. Orijen and Evo are awesome, but very expensive. Before Grain? It's made by Merrick. NB is usually used by dogs with allergies... so that's probably why it doesn't have adequate protein for certain dogs.

These are all high quality foods

This is BG
(This is the Buffalo, there is also chicken and salmon)
Crude Protein (Not Less Than) 32.0%
Crude Fat (Not Less Than) 15.0%
Crude Fiber (Not More Than) 3.0%
Moisture (Not More Than) 11.0%

Did you try the Blue Wilderness or just the Blue Buffalo. If not, I'd try the wilderness

Crude Protein (min)42.00%
Crude Fat (min)16.00%
Crude Fiber (max)3.00%
Moisture (max)10.00%

You could also try Nature's Variety Instinct. There is Rabbit, Duck/Turkey, and
chicken.
Goes from 35-42% protein and about 15% fat.

Wellness Core

34% protein, 14% fat

Solid Gold Barking at the Moon

42% protein, 20% fat