these are the instruments. supplements and ph tuners i use. i use the biobizz ph up and down to adjust the ph. currently the soil is only biobizz lightmix straight out of the bag.No it is not. Biobizz Lightmix is just a blend of peat, peatmoss and perlite, and some pH corrector. It will never take you throughout of veg and it is designed to be used with their nute lines. Now I'm not saying you HAVE TO buy those, but you need to use something from which you know can work with this substrate.
The EC of this is largely due to the amount of nitrogen, there's very little P & K in it, and some other stuff may also lacking. That in itself is problematic because Cannabis needs also quite some Potassium to hold water, I mean you can see how some of your leaftips are dry from the outside.
Could you also tell me what you've been using to pH down and if you are firm on the equipment. It's just one error on one step somewhere and then this single culprit can take the whole grow down.
You can use BB Lightmix in a mineralic setup and thus treat is like soilless. You need EC & pH meter for this and a 2 bottled liquid nutes plus Calmag.
You could also buy just Bio Grow and Bloom from Biobizz, plus Calmag.
Or you go the way to implement dry fertilizer into the Lightmix and you could either use Osmocote for a mineralic setup or some manure + some lime. All these approaches are prone to error, and you always gotta measure each step analytically to know with what you're working with.