I have only recently begun training legs individually, and while I have always noticed my left side is weaker then my right, the disparity during this morning workout was crazy. I do single leg, leg presses (one leg on the ground) and I noticed that where my left leg wanted to give after 5 reps, my right was barely struggling.
So do I keep the same regiment? Give the weak leg extra does?
This lift is post Squats and Rom. Deads. Just to forestall this post getting deviated. 
uhm do you do the 5 reps with your left and then do 5 with your right or continue with yuor right till almost failure?
I always do equal reps, but where the left is ready to quit. The right barely feels used.
well if you’ve been doing it for long, i guess you could like do your normal lifts with both legs when you have to and then do only with your left leg those exercises for a while (i guess around a month)
if it still doesnt work, i guess stop even the normal lifts for a while and only do left leg.
idk what else there is to do!
Do the same amount of single work for each leg. You might also want to stop bilateral leg work.
Try Bulgarian Split Squats.
I already do the Split squats one day per week, alternating with static lunges.
Leg Day 1:
Squats/Rom. Deads/Leg Press, Single/Calf Raises Elevated/Static Lunges
Leg Day 2:
Squats/Rom. Deads/Leg Press, Single/Calf Raises Elevated/Bulgarian Split Squats
Start off with the single leg exercises (BSS / lunges) instead of squats, and always start with your left leg. Try that for a while, see if it helps.