As has already been mentioned, stick to his kibble and forgo any other foods or treats.
Try putting some of his kibble in bed with him. Often if they aren't feeling well or when in a new home, they will eat if it's right there in bed with them.
The yucky poops are probably from being in a new home. If he'es having frequent liquidy diarrhea, that is a concern. Soft greenish poop is most likely just from being in a new home. You can check to see if he'es dehydrated by lightly pinching some skin and then release. It should go right back to normal. If it doesn't he is dehydrated.
* * * Nancy * * *
Retired from breeding
Rescue contact for both the Hedgehog Welfare Society and the IHA
Rescued over 70 (and counting) hedgehogs needing a new home