What type of problem is this?

Yellow burnt leaves is a sign of plant not able to absorb potassium. Most likely from nitrogen overdose. Sour/acidic soil is a symptom. Most likely cause is that the soil is already fertilized. Adding more fertilize probably tip the plant over to burn side. Danger is that roots will be damaged and plant slow down until root is recover. Fix - I would flush the plant. Rinse the pot with a couple of gallon and let it dry for two days. To fix toot - dose with root stimulant once. Too much will also kill your plant. Cannabis is a weed. Less is more.

The leaf curling is typically caused by humidity. The other symptoms could also be explained by humidity/ temperature problems. But, in your case, there seems to be a few different deficiencies presenting which would indicate ph fluctuations as the cause. Over-fertilization can also have this effect. If you are using advanced nutrients, you have to go easy on the amount you use. Do not follow their suggested dosing guidelines- they should be cut 1/4- 1/2 strength. Make sure you are testing the EC of your feeds and keeping under the suggested amount. PH with advanced nutrients will also be fairly basic and ph down will need to be added during feeds to keep ph around 6-6.2 for soil.

could be several things but first look in my experience is nutrient lock out! Usually caused by PH level to high! Aim for ph range of 5.5 to 6.2 to recover half your nutes and compensate with a foliar spray of a 1/4 dilute solution! Hope this helps

You need to know you PH, you PPM, your PPFD from your light to accurately help. Off my hip I can see some nitrogen "clawing" on your right hand side plant and the burnt-looking one looks like a cal mag deficiency but I cant be sure. Could also be light burn from a light that might be too close. 45% humidity is low for veg so id get that up 50-60% hum as well.

Bump! Any more advices??

Do you really think that all of this problem relies on the ph?

If you don’t know pH it could easy be lockout. Looks like deficiencies. Grab a pH pen from eBay maybe?

Advanced nutrients used last water was grow micro and bloom 1,5ml each for 1,5l water and i spread that for the 3 plants after 2 days i woke up to this! Im thinking of buying superthrive and a extractor! I dont know about the ph cause my apparel isnt working

And need way more info than that, make a diary

No pictures mate