Growing Bag Seeds & Pineapple Chunk (First Grow)

Hey guys this is my first grow and I'm learning a lot of new things!

So I found two seeds in a bag of particularly nice weed and decided to use them because I was impatient.

One seed didn't make it past seedling because we'd been overwatering them and having the light too close to them.
Running 400w HPS in a 60x60x140cm tent.

It's been 5 and a half weeks since seed and suffered some nutrient burn and heat stress because I'm a newbie and fucked up. The leaves are still starting to claw upwards when new ones start to grow and I'm not too sure what to do with it..

Temperatures are running around 78 degrees F, with relative humidity at about 30% or so. I'm hoping to get a humidifier to increase it a bit - currently using a towel suspended from the top that is dipped in water.
Currently have a seedling from Barney's Farm. It's a Pineapple Chunk. It's been in soil after germinating for about 7 days and it seems to be doing well.

Soil pH is just below seven. Using Plagron Royalmix soil.

I am no expert by any means but.....you should probably change the soil. Looks like it has nutrient burn and if you didnt add nutrients yourself, then it means the soil most likely comes with water activated nutrients of some sort. If this is the case then it will continue to burn your seedlings. Plenty of help to be found here but do a little more research as well. For instance, i watched threads on here for 3 years before even planting a seed, bagseed at that. And i still managed to mess it up. And 30% humidity is not bad, you shouldnt need a humidifier. Add more plants, humidity should go up a lil bit.

55-65 humidity for veg
30% humidity is great for Flower phase not got for veg