If you got him from the same place does that mean you went back to Petstupid?
2 by 4 for two adolescent males is likely too small. You need a 2 by 5 at least with a loft. Since you didn't see (or listen to) my advice, be on the watch out for squabbles in a few months.
And take them both to a
cavy vet for a check up. Petstupid buys them from breeding mills and backyard breeders. They are often sick and missexed.
eta mating and puberty are two different things.
GPs can mate at 3 weeks.