I happened across something about haemophilus Somnus and it sounds just like what you describe. I know you say you vaccinate for somnus but there may be different strains. I would definitely leave something like this to a good veterinarian. And if not the first try another.

H. somnus diseases have also occurred in the ears and eyes of cattle. The ear form is characterized by a large amount of thin, yellowish discharge flowing from the ear canal.

The above is a quote from the piece I stumbled across when filing some things today.

The source is here . Scroll down to the "misc forms" section.

Good luck.

Jim at Dawn