Red Oak with Staining/bleeding

[RedHawkRidge]

This weekend I noticed a few young red oak with dark stains on the trunk bark.  Trees are 5-8" diameter.  When i probed the darkened bark, it was punky -- soft and mushy.
I dug down a ways, and actually released a flow of watery juice in one spot. Yellowy water-like, but had no real smell, nor did the wound.

I dug out as much of the punky wook as I could, shaped the wound in a narrow oval, and sprayed with wound dressing paint.

Any ideas on what's going on ?  The trees appear to be very healthy, and I don't think it's oak wilt.  Should I have left the wounds open to dry out instead of closing them off with the dressing?
Thanks for any help.  Jim