Help with feeding

Can anyone please give advice on feeding a 5 month old rottie pup.
He is currently on James wellbeloved puppy but keeps getting upset tummy, not constant just when he goes its very runny.
Hes otherwise very healthy , lovely shiny coat and wormed regularly.
Any advice please

It could be that you are over-feeding your dog. It could also be the food. I know when I got Buster he constantly had loose stools. I wasn’t overfeeding. I changed his food several times because he always had loose stools. Eventually I changed his food to Wainwrights salmon and potato (hypoallergenic) and his stools are now firmer.

HTH