Leaf Tips Turning White?

[CrazyChef]

So, a few of my girls have their leaf tips turning white. Any idea what is causing this? I have 4 strains going, and only the White Widow and Amnesia are affected. The Peyote WiFi and Blueberry gals are fine.

Background:

• 55 days since sprouted (still in veg)
• Natural organic soil in 5 gallon fabric pots indoors in a 4x8 tent
• Feeding nutes every time I water, which is once every 4-5 days, about 1 liter per feeding
• Mega Crop nutes - 4 grams/gallon first 4 weeks, then 5 grams/gallon since then
• Sensi CalMag Xtra - ~4ml/gallon
• pH average 6.5
• Temp is 70-80F
• Lights are 3x Oneo II full spectrum LEDS, 24/0

 

[Chris Scorpio]

Nute burn

Some sativa can be more sensetive than indica
Drop back the feeding on them

 

[Greenlizard]

I agree with Chris. It's nute burn.
Not all strains can take the same dose. If you alternate your watering schedule to give just straight ph'ed water to the more sensitive plants every 3rd, or 4th feeding or so this might be enough to regulate the difference. Or you can mix separate batches to feed individually as per strain requirements.