Montego Karoo Senior Dog Pellets

My Beagle has been on Montego Karoo Senior dog pellets since July 2017 - no problem. I purchase a 20 kg bag on 4 September 2019 and he has not stopped scratching and licking his whole body and paws for the last +- 5 weeks. I have decided to go to the pet shop today (21/10/2019) and buy another brand dog pellets. I have also noticed mouldy pellets in between the pellets.