This is my first grow, using autoflowers under 540 actual wats in a 4.9x4.9 tent. In Biobizz light mix soil. Grow is just over 2 weeks old and they started shwing browning leaves at the end of the first week and over the last few days more and more of the plants have leaves showing problems. They had their first feeding of biobizz grow 2 days ago as biobizz says to wait 2 weeks before feeding.

I am using tap water (hard water area) and I have a wall mounted fan and a carbon extraction kit. I was having issues with ambient heat reaching up to 35c, however after moving the tent to a different space, I finally have consistent temps of 26-28c and humidity of around 50%.

I really can't figure out the issue on the leaves, I have checked for bugs and it isn't that. I have given them their first feeding and that hasn't helped. I could use some experienced advice.