Yellowing fan leaf tips

Hello I’m experiencing some yellow tips on several fan leaves. Looking for some advice and feedback. I believe this was caused from water with high PH. Two Autoflowers are about 1 month old. One female is about 2 months old.

The details:
2’3” x 2’3” x 5’3” grow tent
(1) marshydro 300w LED
(1) HGL 100 quantum board
-hung about 18-22 inches away from top of canopy

Temps always range from 72-82 F
Humidity ranges 40%-60%

3 gal fabric pots
Bottoms filled with kindsoil, top filled with coco loco medium

(1) female cosmic railway
(1) gorilla glue autoflower
(1) tangerine dream autoflower

Been watering about once every 4-5 days. Rushed last water and didn’t check PH. Left tent unchecked for 2 days and when I checked noticed yellow fan leaf tips that have progress a bit more each day since.

I have been using Poland Springs and Smart Water for my water source because kindsoik required water as close to 6.5 as possible. I have ordered some natural citric crystals to help lower ph of water for future.

Does this look like damage from high PH’d water used?? Or some kind of other defficiency ?

Also interesting that the older, female didn’t experience any yellowing from the same water used on the autoflowers.

Let me know your thoughts !

Anyone have anything? Still need to get to the bottom of this!

Gmcul said:

Anyone have anything? Still need to get to the bottom of this!

Click to expand...

I'll make a couple of comments.

There are probably not many growers who have experience with, Bottoms filled with kindsoil, top filled with coco loco medium.

The top growth looks good. Can't tell if the old growth is continuing to get worse or if it is in check.
The dry leaf damage looks like it happened a while ago.

Not sure if using smart water or polar springs is a good choice. Bottled waters sometimes have added minerals that you might not want for plants but IDK for sure. RO would probably be better.
Good Luck!

It appears you're dealing with an Mg issue at a minimum. Are you adding any sort of Mg and Ca supplements? Coco has an infinity for Mg and Ca.

go with less water and nutrients on led grow light, but add more cal and mag would be good.