I dont always have wood in with my Bristlenose (some have it some dont.) and i dont feed my bristlenose anything special, just what all my other fish eat (colourbits and flake) and every now and again they get trout pellets and/or shrimp pellets. I have had great success with BN, i have multiple full grown males and females and have at least two pairs breeding :-?
Im not sure what has happened to yours, but i dont think it could be anything to do with lack of wood, lack of proper food, pH or anything similiar. I have BN breeding in a tank with a pH of around 6.2, and i also have them breeding in a tank with a pH of 8....
Keep us updated. id suggest keeping the water changes up! every 3-4 days preferably, they dont need to be big, just 10% or so