It’s great that you’re asking questions. You are correct — pellets only is definitely not a good diet. It needs to be a large majority hay (adult rabbits), which just a supplement of pellets and veggies.
How old is he, and is he neutered? This will affect the proportion of pellets fed, as well as the type of hay and pellets fed. Also, unsure if you had a guinea pig-vet, but if you are committed to Buddy as a great pet (which I’m sure he will be!), you’ll need to find a rabbit-experienced vet in your area to take him to for a check-up. Some breeders are more… sketchy than others? Some are not responsible breeders and breed unhealthy rabbits, and some say one thing, such as the rabbit is this old or has this condition, but it’s different when examined by a vet. Rabbit-experienced vet is VERY IMPORTANT. There are so many tales of rabbits who aren’t treated correctly because a well-meaning vet is not experienced and doesn’t know how to examine and check a rabbit.
What bam says is correct. String of pearl poos occur during shedding because rabbits ingest fur as they groom, and unlike cats, they cannot cough up hair balls. It’s important when you see these to begin brushing him daily, as too much hair will clog his stomach pipes, causing GI stasis. Think of it as this: the more hair you brush off him and throw in the trashcan, the less he ingests. You want to really observe your rabbit’s behavior and posture while grooming because some like grooming to a certain intensity/location, while other times they find it uncomfortable/painful if you’re tugging too hard or the brush is uncomfortable.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.