Going to disagree with my growmies here - clawing DOWN would indicate an overdose of nitrogen but clawing UP indicates heat stress... and yeah, it can be the only plant affected by the temps - each plant will react differently to the same set of circumstances. You might want to provide this one a little bit of shade during the hottest part of the day (I'm assuming this is an outdoor grow)...
Good luck!
They are in pretty bad shape pal.
They are clawing to bits
You have overdosed them with N.
And the clawing looks old also. Pull back on the Grow nutrients or anything N rich.
Good luck