No man straight the fuck up this is nutrient burn from your soil.
I know you said you using since day 1, and this just started happening... but I can full on guarantee 110% that this is nutrient burn from your soil and I would transplant out of that shit ASAP.
I am on my first grow too, and I used soil with water release ferts in it too... and for the first 3 weeks my plant was totally healthy.... and then the nute burn kicked in all of a sudden and won't stop burning the shit out of my plant... (have not given my plant ANY nutes whatsoever, just from whats in the soil)
Lack of water definitely not, your plant would just wilt if it needed water... not burn.
Straight up man, its nute burn and I would transplant NOW into organic soil w/ no fertilizer... or else your plant is gonna be in for one fucking bumpy ride.... (and do it now, before it's too late which it is in my case)