No way is your plant had it . Defoliate, Am not mega experienced but people will have varying views about the state of your leaves because it could be so many things. I would add 1 tablespoon of epsom salts to 5 litre of water and and give it a good water , take off all the badly damaged leaves and continue as normal. Might want to give it a bit cal/mag as well and a couple of feeds of grow nutes. People will probably slate this advice but have had a similar problem and thats what i done and it worked. Make sure that the dark period is 100% dark as well. Good luck !