Watch the new growth it kinda looks like it's burnt soil maybe strong DO NOT WORRY about the yellow that is the least of your worries you have a bit of nitrogen toxicity but besides that nothing serious try not to get ocd on it you'll only make things worse. What kind of lights are you running...
To achieve descent weight your gonna wanna invest in a higher wattage led which may be a pretty penny I have a 1000 watt hps bulb I flower with which is a much cheaper alternative to led with the same results but will cost more in the long run on your electricity use.