hi there - i had the same problem ...first kidding this year and our girl annie started scouring at about 4 weeks, the foamy poo is exactly what she had, she seemed ok, just a little unhappy for a week - i put it down to the milk- im feeding caprilac - she wasnt overly ill, so a week past and she was still pretty shitty, so decided to start milking out the other goat and introduce the fresh milk, the problem persisted...
so i called the vet after another few days and she treated for cocci. i thought that it would work, as she was the same for a few days...bt it cleared up and she hasnt had a problem since, and is growing strong. the vet said that they sometimes give the medicine as a preventative, and wouldnt do any harm!
i hope that this helps, as i think it would be worth youre while treating as the vet said like a preventative and if no luck, try the vets again! it all depends on which one you get!
hope they get better sooon, as i know how upsetting it is when you cant fix them!