I don't think it's possible to answer your question about the rights and wrongs of the brand as the two are highly likely to be linked. Pedigrees major ingredient is wheat which a lot of dogs are intolerant to. It also lacks any real protein - which is needed for firm poos. Give scrambled eggs for now to bind him up a bit. I do recommend changing as its obviously not agreeing with him. Take a look at allaboutdogfood.co.uk. Go for nothing less than a 3 out of 5. Look for one with a named meat source as one of the first three ingredients and avoid anything with maize or wheat as many dogs are intolerant. Price is not an indication of quality - there are plenty of poor foods with a top price tag. In my view one of the best price to quality ratios is Skinners Field and Trial as its about the same price as Bakers/Pedigree/Wagg but far superior quality.