My 22 month old son is on the ketogenic diet he consumes nothing of color and is gtube fed a special formula. When I vented him before his last meal, I noticed dark stuff in his tube so I put it onto a piece of paper towel and it is purple. .....almost like he had koolaide which is impossible. He has been having issues with his bowels lately and even passing little bits of blood. Could this "purple" be blood?