I have been diagnosed with Hematospermia which is blood in semen.  I have visited the urologist few times, one time I had a culture then the doctor prescribed antibiotic, it worked for sometimes only then I took a different antibiotic and so far I still see blood in semen occasionally, not evry time I have sex.  The semen color goes from brownish to light or red blood.  I have been experiencing blood in semen for almost a year, checked my PSA good,  I was told by the doctor not to worry and he thinks it is just bacterial infection.  I am 47 years old and I am athletic so my case is very similar to your husband'case but my suggestion is to keep visiting the urologist, like myself until it is all clear.