Well, I don't recommend fermenting 100% grapefruit juice. I think it's too acidic for the yeast to work happily. With staggered nutrient additions, it still threw a lot of sulfur. It's dissipated a bit with age, but it's still pretty undrinkable by itself. Imagine extra-bitter campari, but with a bit of sulfury funk on top.
If I try this again, I'll probably mix the grapefruit juice 50/50 with some grape or apple juice, or mix with low gravity wort.