I feel like it was probably a watering issue. Roots just haven’t been able to search deep and the nutrients have been piling on the top of few inches of soil.
Hope you can fix them, and good luck!! Maybe even consider heavily topping the plants, transplanting into slightly larger pots that are uniform in size. Then hydrate the soil evenly just outside where the transplanted soil meets the new soil.
It might allow the plants to grow/heal, shifting more energy into repairing and allowing you to possible even out the canopy, keep the plants, and have them just veg out longer. I usually water feed every 3-4 days, close to 4 litres of water in a five gallon pot at my current stage.
My tip, but I’m a beginner grower, would be to heavily top though. Cut the plants down to 5 or 6 nodes, and have them just heal up. Might be a good option. Not sure though, fingers crossed