Looking pretty good but if you topped them now at 3ft tall it would be a bush by the time it was ready to harvest, id just keep taking care of it as you have with more attention since your about to put them in the budding cycle. Other than that listen to him. ^ Good luck mannn
I think you might wanna water them more frequently, sometimes I water mine every otherday and mine maintain perfect health. Just experiment with it up with the leaves get worse stop, it might be from the lights being to close to them also, my point being since they're crumbling apart the plants...