Two females are highest risk as far as pairings go.
Very risky to feed them together and definitely to let them get their faces in the same bowl. They should be fed separately - as in in different crates, rooms etc.
Even very bonded dogs are still dogs. Life was tough for their ancestors, and not giving up your food was one of the major traits that determined who survived. So, there is a primal response that most dogs are genetically wired to have around their food. Many dogs are so domesticated and obedience trained, that it's watered down enough that we don't get much of this response - at least with humans, and in many cases not even with other dogs. But it can and does happen, a lot - a dog that is the most friendly, easygoing, benign dog in most situations, once day having a pretty primal reaction towards another dog, cat, even a child around his food bowl, bone, rawhide etc. It just is safer handling to feed them separately.
Beyond that I would look for a rewards-based trainer with qualifications (beyond "I watched dogs and figured them out myself" - a background in psych, animal behaviour, zoology, or accreditation from a legit training course - Karen Pryor, Jean Donaldson, etc). You need someone who knows how to manage the situation using positive reinforcement. If a trainer is talking about being "alpha" and pack theory much, move on - most of the old school beliefs about "dominance" being any motivator for behaviour are disproven time again. Using force or just "outdominating" the dog may suppress behaviours but it will not fix them - you don't know when the spring will uncoil and you'll have more problems - often worse.