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Is this every poo or just occasionally.
About every 7-8 poops will be what is called a cecal poop which is usually brown and wet (like pudding).
A lot of times it has to do with diet. If they have had something with a lot of water content (melons, ripe fruits, etc.) it can be a bit more loose.
Here's a poop chart for reference:
Could have been the fruit.
I would just keep an eye on him and if he has constant loose poop, you may want to limit the treats/scraps to see if that helps, if not worming him would be second avenue to pursue.
Valbazen 1/2 ml orally and then repeated in 10 days for each chicken is an excellent wormer. Fenbendazole (Safeguard, Panacur) is also good at 1/4 ml per pound for 5 days in a row.