not too sure looks like ether heat burn on those tips ive had it before when i used to bake my buds under a 600w at 12'' that could be it with the 28-22 swing whats your ventalation setup?
mate i think you need to ditch the lemon get a water ph meater and get it to 6.0-6.3 and keep it stable .next tabbaco spray is great (at killing ) but its sooooo toxic (get a spay bottle and spay lots of water on theose leafs and make sure its all spayed off) i would recomend getting some live...