Hi! The thing to watch for is the fiber, crude protein content and sugar. Pellets should have at least 18% fiber, 20-25 is best, protein should not be any more than 14% for an adult rabbit diet and calcium should be at no more than 1%.
Binky Bunny has it all broken down here:
https://binkybunny.com/Default.aspx?tabid=60
The thing with the alfalfa based pellets is that they are primarily for young rabbits up to the age of 7 months (Isn’t your bun about that age?). If you feed an adult rabbit alfalfa-based pellets, they can get fatter from them and one just needs to be more restrictive on the amount one gives them and also keep an eye to make sure they don’t get too much calcium (urinary and bladder problems can result). They aren’t the best for an adult rabbit, but are OK, ideally a timothy-based pellet is what should be given to an adult companion rabbit. Rabbit pellets were primarily made for the "stock" rabbit and not companion one and so alfalfa-based is the most commonly found food pellet for rabbits so I’m guessing that they just might be alfalfa based since they were sold at a feed mill.