This doesn't sound correct, op. A 75/80lbs deadlift total is like, the bar plus 15 lbs on each side, a low weight for that sort of exercise. It sounds like you either had an undiagnosed problem, or used incorrect form. Usually you don't use dumbbells for deadlifts, too. As others have said, it's harder to stabilize.A little over 3 months, yeah.
But I was doing high weight, low rep, and not having issues with it. I kept form. I think maybe it was only 75 lbs or 80 lbs. Like 40 lbs dumbbells in each hand. Can't remember, it's been a year since I did any of that.
I used both depending on the day or week. My trainer helped me design and lead my workouts. I would do different variations of deadlift or squat.
Hope you get better.