I am assuming the tan colored dog is the sick one.  You are probably aware that the cocker part of the dog is well known for ear problems due to the way the ear flaps over.  Do you keep the hair on the inside of the flap trimmed short.  It's supposed to ventilate better and lessen the frequency of ear problems.  I have a Springer which can have similar problems, and keep the inner ear hair pretty short.  I don't know if the hair trim is the reason, but no problems with ears. Good luck.