Upper veg leafs purple and droopy

[S3280]

Hello Everyone,

I have a plant which I’ve grown many times before that seems to be having an issue in veg. Can anyone tell me what would cause the upper leafs of a place to turn purple and droop. Please see the pics.

Thanks for your help in advance.

 

[DoctorJohnson]

You have got some kind of major league deficiency there. According to my reading, molybdenum deficiency causes purple leaves, but running out of trace elements is really hard to do!
What are you growing in and what are you fertilizing with? Whatever the case, they need to be fed!

 

[GreenhouseEffect]

Oh wow. How is your temperature, also? Not getting to cold are they?

 

[D.A.A.S.69]

As GreenHouse Effects says, sudden colder weather can do that.