Can’t diagnose my sick plants! Will they live ?

Hi Guys,

I’ve been trying to grow some granddaddy purple autos for like 1 month now, and I seem to keep running into issues.
I thought I had slow growth because the temps were quite cold (lowest I had was like 12degrees, with the average around 20degrees). But I’ve put got a heater in the room now and it’s stayed warm.

But for about 2 weeks now I’ve had almost no growth whatsoever.
I’m using 300watt led light, and I have a dehumidifier in the grow room keeping the humidity around 50-60.
The one plant in the pot I realised was overwatered once, so I stoped watering it for ages to let it dry out. Probably about 3-4 days. I started watering it only a tiny amount every 2 days to let it recover. It’s on 20/4 light cycle and is about 30-60cm away from the light

My issue is with the leaves on my plant, they seem crispy ans dry, even snapping off when I touch them. Could it be oxygen in the soil? Did I not put enough perilite ?
I’ve been using canna nutrients Vega terra + canna boost. I’ve only used 6ml + 1.5ml per 1L of water. And have just watered from that 1L bottle to both. I also have some dynamic lifter in the soil for the extra nutrients.

Can anyone help me, I’m considering starting again because it’s been over a month and they don’t seem to be getting better.

I’d start again bro your whipping a dead horse now especially autoflowers. You clearly know what you done wrong just as you explained. Over watered damaged the roots which would’ve be exasperated be the cold which will limit the effectiveness of the roots even more. Then you feed them with cold damaged roots when they weren’t productive enough to uptake nutes yet. Combined with a blurple light it wasn’t an ideal situation. But if you learn from it its not a complete disaster

2nd that, just start again and don't kill them with love. they'll tell you when they need water and nutes. mellow out and smoke a doob