Leaf edges are curling up...Check my photos, what is going on???

These girls were stunted for a while so they just started growing fasted. It is usually around 80 degrees in the room. They are in 3 gallon pots with soiless mix. Under a 400Watt HPS lamp. They have mediocre ventilation. The soil is at a pH of 8 because I was watering it with tap water (bad idea). I finally bought a test kit and found tap water to be around 7.8 pH. I use brita filtered water now. It has a pH of 6.8. I just used a low dose plant food. My others are being shipped to me now. Can anyone let me know what might be the issue? I water them whenever the soil is evenly dry at least two inches down. The lamp is 30" above soil level. Ask any questions.

had a similar problem healthy looking plants , raised the light and it was sorted within literally a couple of days. i was using a 400w hps too. 30inches is quite high anyways tho maybe more fans blowing directly on the bulb getting rid of more heat. just an idea let me know if it helps....
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Too much heat man. Had the same problem with a 400 watt hps. Checked my temps and was at 90. Get air blowing directly on that light and away from your plants.

When you say the ventilation is mediocre, what do you mean? You should at least have a fan circulating the air around and a way of evacuating hot air from your grow room. I would say that you need to also need to keep the top of the soil moist at all times do not let it dry out until it is established a healthy sized root ball, because all of the little tender roots are near the top of the soil when in the seedling stage. Let us know how it works out. They do look healthy.

They are growing, but the leaves are still curling. What's the issue?

Is it heat stress or what? Please helpppppp

it does look like it could be from heat, or maybe other things as well. Whats the temps??? A thermometer goes hand in hand with growing, along with a ph tester, I think its two of the most important things to have before u even start. When it gets too hot, the leaves tend to curl downwards and 'cup'. Also there wouldbe some browning unless u caught it early. Check the temps, check the ph, and how often do u water?

I have a temp and pH tester. The temp is at a steady 78. The pH is high but I am currently working on that. I water whenever the soil is completely dry at least a finger length down. Thanks for your help!

Okay, I am still confused how 80 degree climate can effect a plant this bad. The leave are "cupping" like someone said. They are in a spare bedroom so its not like they are in a confined area generating heat. How can I get rid of some of this heat? I have THREE fans blowing on the light and one circulating air from outside. What do I do? Thanks alot guys.

maybe the fan blowing on the plant is drying the edges making them curl up?

That might have had something to do with it. I just installed an window air conditioner unit, should take care of the heat. I also adjusted the fans so there is not to much breeze hitting them all day.