Leaf tip burn like that, when your feeding it hydroponically, Is 99% of the time going to be a nutrient issue. It could also be a ph issue, but its more likely your overfeeding it, causing a nutrient lock. Thats why your also seeing signs of deficiency, even though its over fed. It doesn't matter what line of nutes your using, all companys recommended dosage, is always going to be high, a normal feeding for most plants is most of the time a little over half of what they recomend. In your case, id flush the medium with ph'ed water, and I mean FLUSH IT!!. Let it dry out, not completely (never let it dry out completely) but when it looks like it needs water again, give it a 1/4 dose if what you were feeding it, along with a little silica, about 1/4 of what the silicas recommended dose is too. Then work your way up to 1/2 and stay there for awhile and see how it looks, then increase or decrease. Make sure to ph it correctly too. Also, im sure your aware, but just in case your not, those damaged leaves, will not get better. Look to new growth to judge how its doing. Also, be sure to correct your feeding if your giving it too much of something. Everything has to be in the right ratios. Calcium should be at a 7 to 1 ratio with magnesium. Potassium should be at a certin ratio (the #'s escape me at the moment, I wanna sat 12 for some reason) to calcium, and so on, and so on. Make sure all of your nutes, and any addatives you might be using, aren't throwing your ratios off. Also be aware that a PH problom, can look like anything, and certain nutrients are better absorbed, and some are only absorbed a certain ph levels.