You don't always need to go heavy on your seek for bigger, more defined legs. Sometimes volume and time under tension are just what they need to break through the plaetue holding you back. Try this Leg workout on your next leg day and I promise you'll see what I am talking about.
Dumbell Squat 5x20 (Last 3 sets are a drop set with no weight, focus on pushing out on heels to engage quads the whole time)
Leg Press 5x20 (shift to heels at top of movement to engage quads) Superset w/ Hack squat 5x10 (3 seconds down, 1 second up)
Leg extension 5x15 (Focus on getting the back of your knees off the pad)
Walking Lunges 3x30 (Big step and stretch in hamstring)