Other than topping-out the burnt parts... have you done any trimming?
Often, as a plant ages the lowest fan leaves die off as they are there for only 1 purpose--- collecting light! And down under the plant, they don't get much light (or air flow)-- so they die.
Follow the trim guide 1st-- (link below)
Then Flush Your plant "just in case" since it couldn't hurt....
Then follow with a feeding of your nutes at 1/2 stregnth...
and watch your temps and humidity...
all that said-- without pictures-- IMO it is most likely just natural die-off.
Good Luck! Trimming Plantshttp://www.marijuanagrowing.eu/trimming-plants-for-better-health-higher-yeild-t21279.html
No need for revenge, just sit back and wait.
Those who have hurt you will screw eventually themselves; and if you are lucky, God will let you watch!
Through What we create- we are immortal.