That's a large difference, but it's very plausible.
I train Westside for a large part of the year, and usually we work up to a 3-rep set, and then continue with singles. We NEVER do more than one rep on any weight above our five-rep max, when we're training for the competitive lifts. The stronger you get, the larger this difference becomes.
This just means you've got poor strength-endurance.(which most bodybuilders have as a foremost quality, in fact, due to most sets with reps between 6-12)
This has little to do with fiber dominance, it just means you get what you train for.
Start doing sets in a higher rep range, and you'll get there fast.