hi ladies! My DD is 6mo and we are fighting mucous and green poop with some blood for couple of months now. She started to have it after 2mo and it became worse and worse (some mucous at first, then color change, then some blood here and there and once she had severe diarreah). So our doc told me that food allergy needs some time to show reaction. That is why usually at first babies have normal seedy poo, and if they are countinuosly expanded to allergen (through breast milk) then around 2mo it starts changing. My DD was soooo windy until 5mo when I started elimination diet. Her wind improved really fast, as well as she is less fussy, sleeps better, no stomach cramps. But mucous is still there. :(In case your LO has diarreah, be careful, it can be dangerous because of deshydratation, talk to your doc.
So probably talk to your doctor and start elimination diet and see how it goes. I took away most common alergens first (dairy, soy, eggs, nuts, chocolate, wheat), and now I'm taking all glutein away. Hope this helps little bit.