You could be having occult bleeding - bleeding that's too little to be visibly seen, but can be detected in the stool with an occult blood test. I'm not sure if it's worth asking for one of those, but you could consider it. If it's positive then your GI will probably want to look for the cause of the bleeding.
Or just try the probiotics, I dunno. A foul smell could indicate a gut flora imbalance, but if it smells specifically like blood that does sound a bit unusual - I've never had it before to be honest.
Dx Crohn's in June 2000. (Yay )
Tried: 5-ASAs, azathioprine, 6MP, Remicade, methotrexate, Humira, diets.
1st surgery 20/2/13 - subtotal colectomy with end ileostomy.
2nd surgery 10/7/15 - ileorectal anastomosis. Stoma reversed and ileum connected to the rectum.
Current status: Chronic flare. Do I have any other kind?
Current meds: 50mg 6MP; Entyvio (started 3/11/16)