To be honest he's probably had them for months. They smell awful and even at their most solid they are still very mushy, and at their worst they are very grey or almost liquid.
He eats well and and a wide range. He drinks the same formula he's always had. He has allergies to egg and one fish, but can tolerate cooked egg. He has no other signs of an actual daily allergy (rashes, eczema, vomiting etc).
Is there a chance this is milk/diary related even though it's been slowly getting worse, rather than him having signs all his life? Or is there something else it could be? At first I just thought it was teething but it's just been constant.