What could this be??

Got a problem what coukd this be only startedvto happen 2 days ago??

Looks like a serious mite infestation. Have you checked under the leaves? With that much damage they'll be easy to spot if it is mites.

I've never seen a deficiency cause anything like that tho there are many diseases pot can get that I haven't had the misfortune to experience yet.

what are ur temps, feed ec, ph?