As long as the are still fairly solid I wouldn't worry just yet. If they get real squishy to where they are slimy and smearing. Then I would worry. Try giving him a small burnt piece of toast (like the size of a shreaded wheat) and pick up some Acidophilus tablets. Monitor his poo.
I have had our chins poo get large once in a while. But within a day or so it settles back down. If it doesn't go away, or gets worse, you should take him to the vet.
p.s. I would cut out the raisins. We used to feed them too,and they loved them, but they have alot of sugar in them and can upset their stomachs. We now give them some pieces of crushed rose hips, and they go just as nuts over those, and they are alot healthier too.