COCO COIR Brown spots on leaves

[NewGrower2024]

First time grow ever. Is white widow photo in canna coco profesional, i.m in week 5 veg and i have this brown spots on new and kinda old leaves. I use high fertigation 2 times per day ,general hydroponics trio nutes.Temps during day 28-29°c and rh 67-71. I have a mars hydro grow kit with fc-evo 3000 300w set to 620 ppfd.
Inflow Ph is 5.8-6.1 and ec 1250 with a runoff of ec 1203. Could this be cal/mag issue? I water every time with cal/mag and always runoff 20%. I already cut the affected leaves 2 times but the problem keep coming back. Should i try feed(nutes) and next feed to replace with just cal/mag water with ec of 1250 and ph 6.3? Or should i feed and next feed replace with with cal/mag foliar spray ec 1250 and ph 6.3?

https://imgur.com/a/UkQoUiD

https://imgur.com/a/09Cx1pk

https://imgur.com/a/ffC06dd

[Bluey]

Raise your pH a bit above 6.2. Reduce PPFD until it recovers, say around 400/450. Your temps are high and your EC is very high. RH is fine. I didn't check your pics. I don't like links.

Edit. Give first few feeds at 6.3 then down to 6.2 the next day. If your EC is 1.2 raise it to 1.3/4. If it's PPM it's too high.