Since they’re 6 and 5 months now, you should start switching them over to timothy or or other grass hay. Alfalfa is a lot yummier than grass hay, so they might not be happy about it, but it is very important that they get into good grass hay-eating habits. Grass hay is the most important part of an adult buns diet. It is important to keep an eye though, since some buns that are used to alfalfa will refuse the grass hay. If that happens, you could try and do the switch slowly, by gradually mixing in more and more grass hay.
Show pellets are not ideal for adult pet buns. They are designed to make the buns grow and put on weight and get a lush shiny fur fast so they can be shown and win prizes. They are not designed with the buns’ long term health in mind and they’re too rich for neutered indoors buns. Since young buns do need rather rich food, I think now would be a good time for you to wean your buns on to a quality brand designed for pet buns, such as Science selective, Sherwood or Oxbow. Do the switch slowly, like 3/4 “old pellets” and 1/4 new the first week, then 50/50 for one week, 1/4 old to 3/4 new for one week. This is to prevent stomach upset, buns can get gassy from food they’re not used to, and gas can be very painful for them.
You can use the remainder of the show pellets as occasional treats. If you have a lot of show pellets left you can keep them in the freezer and take out small treat servings as you go. Pellets keep a lot longer in the freezer.
Some commercially available treats sold for buns are definitely bad, but not all are bad -there seems to be a trend towards healthier treats thanks to bun owners becoming more aware. Avoid seed bars, dried corn, yoghurt drops and sugary stuff like dried fruit. Read the ingredient list and nutritional content on the treat packages. You can otherwise simply give them their show pellets or a few pellets of a different brand than their usual ones as treats. A thin slice of fruit or a carrot “coin” is ok a cpl times a week. Fresh herbs are great treats, this time of year you could perhaps even grow some yourself.