I have a disclaimer too: I am new to Bunnies but a professional dog trainer, so all advice is based on my knowledge of learning theory and animal training, in most cases it is the same for all animals, there care and needs are just different. But if someone with more experience gives you different advice I wont begrudge you listening to them haha.
If this was a dog my advice would be to manage the environment so the dog cannot practise the unwanted behaviour. Animals, especially when young and adolescent (like us really) develop habits quickly, once a behaviour becomes a habit it is much harder to stop. Where as if you manage the environment while the animal is young, and they never get to practise it, then as they get older you can gradually give them more freedom and they are unlikely to begin practising that behaviour because by that stage they have developed other habits such as using their own provided toys and cardboard boxes etc.
So if I were you, I would be either placing cage/play pens around the entire edge of the room like you have done with the one spot already chewed, or I would be moving Chestnut and Jackson into a play pen for the time being until they are a little older and have learnt to play and chew on their provided toys. And I would continue to provide daily enrichment, but I would also rotate their toys/boxes/chews, and I would be offering their food in new and differing ways to keep them occupied, ie: pellets in a food puzzle toy, or pellets/greens for training, so on.