Hay is the most important thing for a rabbit’s diet in order to be healthy and it is what makes poops dry, as opposed to wet. Also, at his age (4yo), he actually shouldn’t be getting alfalfa hay — just timothy. Alfalfa hay (and alfalfa-based pellets, if that’s what you’re giving him) is much more dense in nutrients, which is needed for young, growing rabbits, but not for adult rabbits. This may be leading to excess cecotropes that aren’t being eaten and so, perhaps smeared or something on his bottom.
Re: the treats, any non-hay food items are going to deter a rabbit who doesn’t naturally eat a lot of hay, so I would really limit how often throughout the day non-hay food items are offered. Imagine a rabbit being like a child — if they are fed a candy bar regularly throughout the day, they will gladly not eat salads, even when they’re hungry, because they expect something better will come later.
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.