I used to have low magnesium and potassium. I can't eat ANY vegetables at all thanks to chronic pouchitis and a very easily obstructable danger-zone of scar tissue near my old stoma site (in a good year I have maybe 3 obstructions that I ride out at home; in a bad year I may have as many as 16, and be hospitalized 4 times).
Because of this a lot of good, natural sources of potassium and magnesium are off the menu for me, so I have become basically addicted to coconut water as a solution. I have at least one every day. Great source of both, and very hydrating to boot.
Might be worth a shot.
I just wish the cost of it was applicable to my deductible!
Good luck finding a solution that works for you!