troubleshooting, pumpkin ale, and saf-04

so a while back, i made a pumpkin ale. i used a few pounds of actual pumpkin (frozen and leftover from last year's batch when i just got sick of roasting multiple batches for 45 minutes when i realized i only had a tiny cookie pan for roasting anything on in the house) in the steep, and some pumpkin pie filling in the boil. it was hopped very moderately (like under four aau in the bittering and a half ounce of i think fuggles in the nose).

anyway, i brewed it with a friend who was leaving town for a few months, and i wanted to keg it and also bottle a few bottles. this seemed like a pain in the ass, so i procrastinated, and it was on the first yeast for 3-4 weeks.

now it has a weird vegetal taste that's kind of musty. it makes me think of cucumbers and celery and musty basements in the summer. i think the beer is pretty ok, but this off flavor is kind of killing it for me. i used saf-04.

any thoughts?