Help! Leaves Curling Under!

The tips of my plants, which are a weed and a half from seed, are turning brown at the edges and curling up! It started slightly about 2 days ago, and do to unfortunate circumstances I dont have a timer and had to leave the lights on for 2 days until now... but they are just fluoros. Also, I started the plants using Miracle Grow potting soil...

So, is it nute burn or did the plants get too much light? I'm also battling something in the soil which I'm pretty sure is powdery mildew because I water the plants every 2-3 days and the soil stays plenty wet with this watering regiment. Need any help I can get...

flush the fuck out of it without any weird watering agents, get it in a good vented area and keep in the dark for 36 hours before returning it to a regular light cycle, how close are the lights, whens the last time you watered it and with what concentration of nutes for how long?

I dont use nutes... esp since its in miracle grow potting soil. And uh, watering agent? You mean like WATER? Mk.

If they are still young like a week and a half. Try to use just 18/6 lighting. Dont water it too often if it is the miracle grow moisture control soil. I'm using the same stuff and it doesnt need much water I notice. Every 3 days or so. If you didnt mix and break up the soil real good when you potted it maybe your roots just hit a pocket of fertilizer and took a little too much in. Don't add any nutes too it. Keep your lights 2-3" from the top of the plants. Get a little wind blowing on it too. Not much yet, just a little. Dont water the actual plant either, the lights will burn the plant if they are wet. Just water the soil. The soil seems to work well for me. I dont add anything but water and I don't check the PH either.