when a new season starts i basically just take the soil from the last year, fill them in pots and plant the seeds in there. the only thing i do is to cage the plants against birds for the first 2 or 3 weeks. had never problems with low temparatures even with light snow. of course they germinate...
i see a fan in your pictures and it looks like a fixed one. therefore it could be windburn which means the air is blowing constantly on an area of the leaves and they dry out because they loose to much moisture. my advice is to use an moving fan.
just a guess