Failed Hemp Milk-getting annoyed

So, I decided to trial Evan on hemp milk. I made it myself from hulled hemp seeds to ensure there were no perservatives or anything else. I had been giving him the seeds mixed in with the Neocate Nutra. He did fine for 8 days. Then he wasnt too interested in them, so I stopped for 3 days. Today I made the hempmilk and he drank a little. 2 hours later he projectile vomited while I was holding him. It was like the peaches though. He played in between vomiting and only did about 4 times. This is so frustrating. I would have thought hemp of all things would have been ok.....dont know what to trial next...