What is wrong with my plant?

Hello!

I have a 3 weeks old Northern lights under 70w CMH in a PC box.
Temperature 78.8 RH: 47%
Soil: PH 6.2 , 150-300 mg/l N, 200-400 mg/l Phosphate, 150-350mg/l K2O

I only watered my plants with water so far and the leaves are turning crispy brown.

Is it a nute burn or could it be that the leaves are burned because the intense light is bouncing off the car windshield reflector?

Thank you for your help!

Its becoming def and the soil hasnt got much left, start feeding it.

Phosphorous deficiency. Agree with Buds.

She's hungry, I give you five stars for waiting till she's hungry before you feed her, most people kill their plants with food. It won't be long before you can see she is hungry before she's starts eating herself. Good job man it will be a good grow for you!

Completly forgot that she will use the nutrients in soil after 3-4 weeks Thought of everything but that.

I added 1.25ml of Hesi phosphorus plus (8% Phosphorus, 4% Potassium) to 500ml of water and a few chicken manure pellets.

Hope this will be enough to stop the spread of drying leaves.

Thank you very much for quick help!

First of all u gotta look at the very first signs of any leaves looking like anything but pure dark green and then adress the issue sooner because then if u let it go like this it will certainly bounce back as marijuana is extrememly resiliant but it will b stunted. This is certainly a case of nutrients being completely eaten up in the soil and the nutes u r giving it arent at all what u want in this crucial veg statge. Take my advice, clip off all the effected leaves or atleast the dead tips of less damaged ones. then mix about 2 tbl spoons of bat guano in the top layer of soil and mix a very light dose of some good veg fetilizer thats easy to use for begginers like fox farm grow big and leach it down through the soil with a good watering, let dry completely and then no nutes next water. once evry 2 weeks add bat gauno to top layer of soil and u can continuously add higher amounts of veg fertilizer evry other water as well. feel it out,if u c the tips of any leaves ever get burned then back off the nutes and cut off the burnt tips. Dead tissue just makes the plant shift all its energy into heal mode vs grow mode if u c what im sayin. Definitly not light burnt, that would b at the top of the plant, Hope this helps

P.S I would strongly suggest checking the PH as well to make sure ur not starting to get nutrient lock as well