Brown spots on some leaves (first grow)

Hey guys !

I started my first grow a month ago, and everything seems mostly fine for now.

Here's a pic of the babies, I think they seem pretty healthy... ? The 2 on the left are Runtz, and the 2 on the right are Crystal White.
The smaller one is a week younger, one of my seeds didn't sprout and I had to start an other one.



First question : should I be worried about those curly leaves on the smaller one ?



Second question : since a week or so, I noticed brown dry spots on some leaves (see pics below), 2 mostly, but it started on 3/4 others too.

Any ideas on what it could be caused by ? From my internet researches, it seems it could be related to a fungal infection ?





Some additionnal informations :
- I'm using BioBizz starter pack as fertilizers, and I'm following the calendar they give for quantities.
- They're under a LED full spectrum light, a MarsHydro TSW2000.
- Pots are 18L, and I'm watering with 1.5 to 3 liters of water / pot every 2-3 days.

Feel free to ask any futher informations required, and thanks for your help !!

hell yes congrats those darlings look fabulous for 1st or any grow! about the one leaf vs super leaf definition and size/shape. Either its over nut or over/under water. more info to get real reply needs.Id say keep doing what your doing if that grow improves. spreading bad leaves probley over nut but we don't know if you overwatered causing same. the pictures kinda suck but they usually do so the lighter color is maybe fine and the picture taker sucks. idk?

What medium is it?