Oh, I don't agree with the diagnosis of nitrogen toxicity... you're not providing enough nitrogen with your bloom nutes to cause that! Clawing can occur for many reasons, some - like wind burn - aren't a concern here. You are either watering them too much or watering them too little...both will lead to this condition. The happy part is that it's easily fixed and your plants will respond almost immediately to a change in your routine. How often are you watering/feeding? Do you let the soil dry out before another water/feed? If the soil isn't waterlogged, then the problem is you aren't watering enough. Plants, as they age, will require more frequent watering/feeding! When you give them water/feed, make sure you get about 20% runoff - and then let them dry completely (pot really light) before giving them another dose.
Good luck with the grow - this isn't something to be overly concerned about (like nute deficiencies/toxicities or PH imbalance) ... Enjoy the grow!