Just an update incase people have similar worries.

I took max to the vet this afternoon and the vet has given me some sensitive food to try him on as he may have an irritable bowel issue. He's also asked for a faecal sample to check it isnt a bacteria. He didnt seem overly concerned as max is fine in himself, eating and drinking, and not vomiting - so we shall see if the sensitive food clears it up, and just keep him on that if thats what it is.

£90 worse off but more at ease!