Mine was actually a chocolate agouti with a ginger band (more of a double chocolate Oreo). Pemba was actually meant to be a foster to keep Oreo company, but I couldn’t bring myself to give him up after Oreo passed.
Sounds like a good diet. I believe young guinea pigs can have unlimited pellets actually and they also have a fair bit of vitamin C added. I feed Burgess, not the best, but my piggies would never touch anything else and Pemba gets 1/4 cup in the evening and 50g fresh veggies every morning. Have you tried every colour of pepper? I know mine have never liked green as much as red/orange/yellow. I think kale and spinach also have high vitamin C content, but spinach should be fed in moderation. You can also feed broccoli, Savoy cabbage, trimmed green beans and Pemba loves mint (apparently most don’t). If you wanted to try a more natural treat, flaked peas seem to be universally loved and are good for taming (e.g. for the pups) or maybe a bit of fruit?
Finally I just thought I’d attach
this link to a very comprehensive guinea pig safe food list so you can find some new veggies for Chunk. It’s been very useful to me over the years and actually has suggestions for how often each should be fed.
The weights shouldn’t be an issue, if Oreo is pregnant then it’s probably not a surprise if she weighs more and Chunk will probably catch up. Healthy males can weigh 0.9-1.3kg on average (you can see if they actually look over or underweight). Pemba weighs in at 1.3kg but looks healthy and my lightest was Toffee who weighed about 1kg. As Oreo got older he dropped from 1.2kg to about 800g but he had a lot of health issues and could never put the weight back on.