My second grow, might need some advice

[danber]

Hello there!

This is my second grow. My first with only auto strains, 2 Think Different and 1 Automazar. I´m using a DR60 with a 250w HPS.
I planted the seeds in soil 17. August, so they are about a month old now.
I´m using Plagron Bat Mix with 30% extra added perlite for 2 of the plants. And then i have one TD in Plagron Light Mix. 11L pots (3gal).

So, to my problem. When the plants were a few days old, i managed to drop my PH meter to the floor, the glass bulb thingy broke, so i had to order a new one which i didn´t get before last week. But in the meantime i had to water my plants without checking the PH, my tap water is 7.0. And last week when i got my new PH meter, i regulated the PH to 6.4 and watered them with that. And now, some of the leaves on the plants in Bat Mix are starting to get yellow spots.
I have been searching around, but damn, it´s too much information out there....
This is PH fluctuation, right? Or do you think it´s something else? I know one of them is a little heat stressed, but i don´t think that can cause the yellow spots

Bad photos, i know. I can take some new ones when the lights are off tonight

 

[Antics]

Temperature at canopy?

 

[danber]

Temperature at canopy is 26-28c (78-82f), humidity around 50-60%

 

[Antics]

Heat stress was my first guess to be honest. But temps aren't too bad.

How far is the light from the canopy?

Is this problem only on the top leaves, or lower leaves also?

 

[danber]

The light is 30cm from the tops (12 inches)
I just learned that heat stress actually can cause yellow / brown spots, the leaves are slightly curling upwards as well, and the spots are only at the top leaves. Seems like everything is pointing towards heat stress after all. I will try and raise the lamp a little more.
Thanks a lot by the way, i´m still new in this game, so mistakes will be made.

 

[Antics]

That distance isn't too bad for a 250w HPS. But that particular strain might prefer a slightly cooler temperature. Every strain has different tolerances, and even further, different phenotypes of the same strain can have varied tolerances for heat, moisture, nutrients, etc...

From this: What distance should my light be from my plants? I'm seeing 30cm/12" is acceptable for a 400w HPS. So We can try to leave the light where it is, and see if you can improve ventilation.

You're welcome. I like posting in these topics to help folks out with problems so I can learn myself. I'm only on my 3rd grow now lol. So you are going to learn A LOT as time goes on.

 

[danber]

I´m actually waiting for new exhaust fan as we speak, the one i have is supposed to be strong enough for my tent size. But it´s a cheap crap fan, unbelievable loud. Sounds like a vacuum cleaner is running in the room. The new one is much stronger and still more quiet.
So the ventilation will be improved, perhaps that will do the trick

 

[Antics]

Awesome man, just keep an eye on the leaves. And if possible, you can open the tent during lights on to help keep it cooler for now.

 

[kraw420]

I think you where right with your diagnosis. You should have slowly brought PH'd water down a couple points at a time as opposed to a complete leap. I am not a 100% but it does look like PH stress IMO.