[WHIPEDMEAT]

my vote goes on high EC in the half filled pot with that peat or coco, too dry and salts accumulated in it. all leaf tips burned, and curling down looking weak. surely underwatering symptoms to me
check for the run off Ec, it will be over 2.5ms that s sure

[Chrono2]

Seeing as your a new grower MAKE SURE YOUR MIXING YOUR NUTES IN THE PROPER ORDER
nitrates before sulfates.

cal mag goes in first, then your micro, then grow ,then bloom (assuming your using GH basic nutes)

cal mag and micro nutrients should have no sulfates in them at all, grow might have some and bloom should have all sulfates i believe.

basically just make sure your mixing nutes in the proper order NITRATES BEFORE SULFATES.
also these folks are telling you to use sulfate based mag, liquid cal mag is nitrate based.

[Chrono2]

if you have been messing up the order of nutes, i advise you flush with JUST ph water, then start feeding again.
if your not worried about over watering you might even consider flushing and immediately feeding

and all this is assuming your growing in some kind of coco mix

[Chrono2]

sorry for the triple post, but the size of your pot also looks really small for that size of a plant, maybe its just the camera angle, but if you could let us know what medium your growing in and how big of a pot that is we could probably help you more accurately