Leaf tips burnt?? Unsure why??

Hello everyone,

Ive done a bit of research but cant quite understand why my leaves are doing what they are doing.

I stopped giving them both nutes approx a week ago as they will be ready in 2-3 weeks.

Where I am there has been a few very hot days around the 40 degree celcius mark.

The plant in the 2rd pic seems to be fine which is right next to the other with the problems.

In anyones experince does nutrient burn take time to set in??

Could this be happening because of the change to no nutes??

Any pointers or help will much appreciated.

Those burnt time look old. The burn won’t go away.

also looks like heat stress with the taco shape leafs. High heat causes more water uptake. I turn more feed, probably how they. Got burnt