Activities for corgi

Hi 'yall. I have a 5 year old welsh corgi that shares our home with a 9 year old Golden Retriever and a 2 year old Yorkshire Terrier. For the most of his life, my corgi was happy with my other dogs -- although he always has tried to herd the Golden (#corgiThings?) and plays very well with the Yorkie, but recently he has been getting grumpier and grumpier to the point of being aggressive to both of the other dogs. I am always correcting him and trying to give him positive reinforcement when he behaves, but it wasn't working. I though maybe he's in pain but the vet couldn't find anything wrong with him, although one of his back legs goes numb due to how he sometimes lays down and the vet just said he needs to loose a little weight, but he runs and jumps like a fine potato. I am thinking he might need more activities (ie. work) to help him with his energy and weight. But I wanted to get some input and advice from other corgi owners. Outside of walks and the other usual activities (have a broken foot atm 🫠) what other activities would you recommend to keep a corgi active? Also, any other advice would be welcomed as I want to always see my loaf as happy as he can be.