Anal glands for sure, we had two malteagles [malteseXpocket beagle] at my mom&dad's and they were both prone to needing their anal glands drained every so often, a really good sign is when the try to chew on their bum&drag it, it'll be swollen and red around the hole. Also if his poo is getting in his bum hair, get him a sanitary trim
you'll be able to do it yourself once you watch your groomer do it, it's usually pretty cheap to get just the bum hairs trimmed up!
Also, your vet can show you how to drain the glands yourself to save you time and money especially with a vet that isn't open at your convenience... if you can stomach doing it... my mom did it for our malteagles!