How much grazing do they have? And are they shut up in their pen at night, or free to come and go?
Without seeing them, knowing the situation (including whereabouts you are - what country and what area) and knowing the farmer, it’s hard to know whether his experienced eye tells him they’re lacking something, or quite why he would recommend all those things. If he’s suggesting glucose he may think they’re really quite run down. Or I wonder, was he suggesting the block instead of the sheep mix and salt? If the grazing is limited, he may think the balance between forage and hard protein has affected their digestion, and the glucose would help knock it back into kilter. Thereafter, a feed block they can lick at throughout the day might well be better for them than hard feed once a day.
If you aren’t planning to breed them, and they have access to sufficient nice grass 24 hours a day, and you don’t live somewhere extreme like the top of a mountain or a desert, then if they’re in good condition to start with they shouldn’t need any hard feed at all and certainly no glucose.
So as Womble says, we need to know a bit more to be able to point you in the right direction.