Leader- yellow, strange

Hi friend, I actually think that it is an excess of brightness that is ruining these excellent shoots....remember that too much is not always a good thing😎

could be to much nutriants and to much water, your soil is for a to long period of time to wet. We need more infots to help you buddy.

https://www.growweedeasy.com/cannabis-symptoms-pictures When you get to the link above, save it, you're gonna need it. They have remedies. DIAGNOSE IT YOURSELF. Sucks at this stage. FLUSH and get the bad juju out of your medium first. Then get your soil right. Right now you can forget the dream harvest. Assuming thi is not a virus think about cloning if you want to keep the genetics or, perform a reveg and revert back to the vegetative stage. https://www.growweedeasy.com/re-veg-monstercropping

It had to say.Its unlikely to be lack of calcium and magnesium in the mudium as theres planty in your food.It can get locked out for a number of reasons but cal-mag rarely helps.Its impossible to say and anyone saying it is 1 thing or another is nothing but guess work.Check the basics.PH,temp,humidity.Too/wet/dry.Correct nutrition.Theres certainly something to be said for the KISS aproach.Keep It Simple Stupid.They do very well on very little but a little too much and.....

Looks like some type mosaic virus. If you smoke cigarettes do you touch your plants? However, when you went on holiday did you overwater the plant in hopes it would hold until you came home? Brown spots, burnt marks, and leaf scorch can be triggered by overwatering. These symptoms are commonly mistaken for a calcium deficiency, ph problem, or light stress. In these cases, the symptoms often get worse after watering. The leaves curling up at the ends is another clue that this may be the result of overwatering or root issues as opposed to something else.

Looks like there is a multitude of things all happening, very hard to get to a root cause without a diary and history to go on. One thing for sure is there alot osmosis stress happening on those tips, EC/Salt build up must be high. Something defo screwing with calcium, magnesium and pottasium, but given how antagonistic the big 3 are, it becomes near impossible to whittle it down to root cause until you get your pH and EC recorded and in range. I'd wager its above ph7 due to salt buildup. Whether or not that's due to overfeeding or lack stomatal conductance is impossible to discern without diary and environmentals. Gluck.

A bit more information is needed for a better answer. Could be caused by lights, underwatering, nutrient burn, if you were on vacation, neglect.