What is the cause of these yellowing tips?

[Orion64]

Hello, I am new to the forum and this is my first grow. I have one White Widow plant in 90% coco, 10% perlite. Lighting with HPS metal halide for now. Temp between 20 and 23 degrees. Tap water and Nutriplex (almost identical to flora grow.) I have also given 1/4 teaspoon Epsom per gallon. Feedings now at 1.2ml per 2 liter of each nutrient (micro, gro and bloom). PH is at +-6. I have a pen.

I am getting necrosis on the the leaves. Starts with yellowing on new leaf tips and then progressing as in pictures below.

I have cut back on nutrients completely (thinking its nutrient burn). Have only flushed two times past 10 days. I am thinking its either nutrient burn, nutrient deficiency? or N deficiency?? The newest top leaves show signs of starting to yellow at tips.

Your advise will be appreciated.

Halfway Down: Plant Troubles - 420 Magazine Photo Gallery

1/3rd from top: Plant Troubles - 420 Magazine Photo Gallery

New leaves at top: Plant Troubles - 420 Magazine Photo Gallery

 

[NuttyProfessor]

can you drop the ph to 5.8 , looks like it had a little nute burn , and flushing it twice in 10 days will knock it back a bit ,
its not to bad

 

[NuttyProfessor]

 

[smokeyjoejoe]

Looks like nute burn what's the EC of your feed, its not nitrogen deficiency as the leaves would go a pale yellow colour the look burnt, cut back on the nutes, also how long you been in veg for?????

 

[Orion64]

Thanks for all the replies! So quickly!

I will calibrate the Pen and drop back to 5.8.

Plant is about 7 weeks old. Not sure what EC stands for??

 

[Orion64]

Given that it is nutrient burn, what should I do now? Just flush with 5.8 pH water, or should I add some epsom as well? Also, for how long should I do this before adding nutrients again? I'm guessing I need to add about half of the nutrients previously added when starting nutrients again?

 

[NuttyProfessor]

if you flushed twice it should be ok , just dont feed as much , less is more when not in soil , give half strength , those leaves will not go back to a nice healthy green so keep an eye on new growth , if its looking good then she will be fine

 

[Orion64]

Okay, I will leave for now and give nutrients at half strength from this weekend. Thank you for the help.

BTW, I do not have a meter to measure EC unfortunately. Will keep post up to date

 

[Orion64]

Just to give an update to this post. The one flushing did the job. My white widow is now growing out of its pot and is one heck of a healthy bush. Thank you for helping me saving my plant!