OK...back to the Health Food store. Get some Caprylic Acid (not sure if I spelled right) in capsule form. It is very effective as an antifungal is yeast is suspected. It worked just as well as Diflucan, meaning it is effective against systemic yeast. When I use it I mix approx 1/5 to 1/4 capsule in the forumla at every feeding the first day, then 2X a day for a week.
OH...one thing to check. The outer skin is one layer, and the crop has it's own separate layer of skin forming a pouch at the base of the crop. Try and gently pull the outer skin to see if the veins are prominant on the outer skin, or it it is the crop veins showing thru to the outer skin. If in the actual crop then definitely yeast. If also extended to the outer skin inside surface, then there is risk of it going systemic.