Plant is 4 weeks old and starts showing yellow lea...

Your pot is very small for your plant! Your roots can't grow more so your plant can't too :/ Do a transplant for +10L pot and good luck mate

@Clutch Hi mate the droopiness of your plant suggests overwatering your plants roots cannot breath Also I would totally recommend transplanting into a pot atleast 4 times the volume of the one your are currently using reason is haze varities can get bloody big and that little pot just won't be enough So I would transplant into a bigger pot with the same soil mix and allow the soil to dry a bit between waterings to allow your roots to breath Hope this helps

Looks like your issue is overwatering. Most quality soils will feed for 3 to 4 weeks. The pot also looks a little small. I personally would transplant it to a larger pot.