Purpling, contorting, drying, yellowing.

the yellow and the purple are part of how the strain grows, and sometimes is caused by colder temps at root level, but the curling and dried up leaves come from a ph issue, this probally started sooner in the plants life, i would guess you thought you fixed it, but when the ph is off in a plants life then you will get funky stuff happening later in the plants life. so i would suggest doing a flush until your run off is at a 6.0ph level. let you pot dry out a day or two, when you feed use a little less nutrients than you have been, also add some cal mag, and if you have kelp, add some as well. kelp will help the plant rebound and get over the stress. as far as the damage to the leaves go, the dries curly ones, that damage is done to them, so take them off carefully. you only want healthy happy leaves on your grow, you will still have a nice harvest as your about 4 weeks away. good luck on the rest of the grow and im sure things will come out fine