Our 6 year old zu has a light brown discharge coming from her rear end ,she has been wormed recently and seen the vet for a problem with the colour of her poo , which is a yellow colour . Has any one had a problem like this or know what it is

It could be anything from the worming medicine being too strong to an infection to a problem with her liver (which is class yellow poo).

I'd get her back to the Vet with a sample.