Help, am I over watering or is it lack of nutrients?

First grow and not going well! Bought 3 white widow seeds, got them all to germinate and the rabbit eat one! he topped another one but its doing ok.
We are having a bit of a heat wave at the moment about 32c so I have been watering them daily, I have a moisture meter and is says everything ok.
I am growing them indoors, normally under a 1000w light in my shed on a 20/4 schedule but I have the builders in and its even hotter in the shed so I am having to move them in to the house 1st thing in the morning before the builders arrive!
The leaves have started to go slightly brown and crisp up, nothing major but worried i am doing something wrong, i’ve read about heat burn, lack of nutrients, over watering, I am lost!!
I am using Canna Terra Professional Soil and added a Guerrilla Tab about a week ago, it said to add 4 but I read somewhere to reduce this amount.
Any ideas?

Looks good and healthy. I would suggest topping it maybe, then it will spread out…

Also throw some lime in the soil, levels out the PH

Don’t top, you’re in flower.

Those moisture meters are useless, go by weight of the pot.
From my experience, anything over deep in the red level on those meters don’t need to be watered.
Let it dry out for a few days after your last water, if you have good drainage, it should be light, that’s the weight you water at.
Pick it up after watering, it’s heavy, that’s the weight you don’t water at.
These plants don’t like to stay wet, they like wet, dry cycles.

She’s showing signs of heat stress and possibly nutrient burn. Pictures dark and hard for me to see tho. Polarized windows aren’t the best light source for cannabis either. 1000w hps?