Leaf problem

Hey guys , have some troubles
Half of my plants(4 weeks veg) shows similar problem with leafs(see photo)
I’m growing in coco+perlite mix, coco is buffered, ph always 5.8-6.0.
EC 1.0-1.2
Temps- 17-20 degree Celsius
Humidity 60%
Tap water(ec 500)+canna terra+ rhizotonic
Any ideas ?
I am thinking about calcium deficiency , but I am not sure

It doesn’t look real typical of a Ca deficiency, but, unless you’re supplementing Ca/Mg (heck everything, coco is inert) it could well be Ca. Add some calmag and see if it doesn’t stop. BTW, the damaged leaves will not recover, though they may survive.

temps man those temps are too cold for cannabis except maybe for the last couple of weeks of flower.