Help: Darkening new growth and yellow tips

[Drakka]

Hi everyone!
This is my second thread about some issues that i’m experiencing within my first grow.

I got a 60x50x140cm DIY box, I had to place it in a room where temp and Rh varies depending on the daily weather, as I got no other rooms to place it.
Light: Spiderfarmer SF 1000 (24 inch away from plants)
Reflective Material: Car Sunshade
Pot Size: 14 L
Grow Medium: BioBizz All Mix
Ph: using a Liquid Tester and Ph- from BioBizz, around 6,5

I got 2 pc fans but had to shut them off because of low humidity in the first days (around 41 RH).
I bought a Humidifier that I need to clean and fill of water every 4 hours; when on, RH is between 55 and 70, but as I wake up late, it lowers down to 41/43 in the morning.
Temp differences between day and night are always small (Around 27 during the day and 22/21 during the night)

I’m growing:
- 1 Jack Herer Auto FastBuds
- 1 Blackberry Auto FastBuds
I know, it’s stupid to grow a Sativa with an indica in the same small space but, too late

Today is day 21 for my cuties, my Jack Herer is doing well but the indica one (BlackBerry) seems to be stunted...
I had overwatering issues in the first week but since then, i’ve been always waiting for the soil to be dry.
Btw, her medium seems to dry slower than the other...
I’ve been noticing darkening new growth this week, with yellowing tips... can someone more experienced than me tell me why and what to do to help her?
(Sorry If I made some writing errors, English is not my mother tongue)

Here’s the Indica:

The Sativa seems to be healthy, she’s growing REALLY fast:

 

[bobrown14]

Steady the course... hard to say if anything is going on there. AUTOs will start flowering any day now that indica might turn purps in flower and that's the darker color I see coming on. The sort of mosaic lighter colors on the leaves is more worrisome to me. Otherwise they look pretty good. Dont let the soil dry out just keep it moist. Once they get this big its hard to overwater but easy to under water you don't want under watering. That slows the growth at this critical stage.

 

[Sancheh]

I think it could be to much nutes personally!!but I'm no expert

 

[Drakka]

Steady the course... hard to say if anything is going on there. AUTOs will start flowering any day now that indica might turn purps in flower and that's the darker color I see coming on. The sort of mosaic lighter colors on the leaves is more worrisome to me. Otherwise they look pretty good. Dont let the soil dry out just keep it moist. Once they get this big its hard to overwater but easy to under water you don't want under watering. That slows the growth at this critical stage.

I see, so about those light green spots, what do you think it could be?
And how can I possibly solve it?
A member of this forum (Pbass) told me that it could be an early Cal/Mag deficency.
I have bought a Cal/Mag supplement as my soil lacks of it (BioBizz AllMix) but I don’t know if it’s okay to use it even if unsure about the potential plant deficency.
Thanks for the help!

 

[Drakka]

I think it could be to much nutes personally!!but I'm no expert

Thank you, as I fed her just once with 0,5 ml of BioGrow per 500 ml, I don’t think it’s the case... but who knows!
Maybe even 0,5 ml is too much for this plant... I need an answer
It’s sad to see her stunted as I only got 2 and planned to stop “dealing with dealers” but growing instead.

 

[Sancheh]

Thank you, as I fed her just once with 0,5 ml of BioGrow per 500 ml, I don’t think it’s the case... but who knows!
Maybe even 0,5 ml is too much for this plant... I need an answer
It’s sad to see her stunted as I only got 2 and planned to stop “dealing with dealers” but growing instead.

Ur probably right!!
Bio allmix does contain 5% high quality ferts so that also coupled with nutes might of tipped her over the edge..

 

[bobrown14]

Thank you, as I fed her just once with 0,5 ml of BioGrow per 500 ml, I don’t think it’s the case... but who knows!
Maybe even 0,5 ml is too much for this plant... I need an answer
It’s sad to see her stunted as I only got 2 and planned to stop “dealing with dealers” but growing instead.

I feel the force