Centre of leaf browning/dying on only a few tops.

[goatlicker]

3 weeks into flower, this started happening on a few of the tops.
Under 400w hps @ 18inchs, 21c-25c lights on.

 

[goatlicker]

Anyone?

 

[Gond00s]

check ph of soil look up soil slurry

 

[goatlicker]

check ph of soil look up soil slurry

Took a soil sample from top and is around 7.2. Didn't want to go digging deep for a true reading. Do you think it's high or low?

 

[joe9000]

could you have dripped something on it,or light bleaching??

 

[Capn-Crunch]

Looks like a calcium magnesium issue to me
Try to get your PH down to 6.2 to 6.5

 

[Gond00s]

Good chance your soil ph is drifting up so just start using water at like 6.3

 

[goatlicker]

could you have dripped something on it,or light bleaching??

It does look a bit like that but the others aren't getting it? I raised the light a bit to see if that helps anyhow.

Looks like a calcium magnesium issue to me
Try to get your PH down to 6.2 to 6.5

I'll add some cal/mag next feeding and ph lower than usual. I'd already added cal/mag about a week n half ago.

Good chance your soil ph is drifting up so just start using water at like 6.3

Mm, no worries. Will try that thankyou.