Sudden vomiting and strong diarreah

Hello,  I have 8 dogs who started on raw 4 months ago.  All did fine since the beginning, except for Oly.  He has trouble eating, some days doesn't eat at all and had stomach issues.  His hair is falling and looking bad, while all others shine in health, and every 2 weeks or so, he has a bit of vomiting and diarreah.  This time, it is quite strong and a bit bloody.  So it really has me worried...we are in Spain, a Country totally oposite to Raw feeding...so of course all vets have called me crazy, and none would do tests...they just tell me to get of raw and start feeding him "normal food" again, which basically means kibble.  i tried it this time, and he ate it, and his stools are getting a bit better...could he be alergic to raw??  I just cant belive that...but if not, what the hell is happening with him?  I feel very guilty and feel that i am killing him... Advices, and opinions very much apprechiated, please...