@barkido1996 your plants are perfect! What you're experiencing is completely normal and good! The plant is in flowering and is feeding off the fan leaves at the bottom. It's a natural process for the plant. Why is this a good thing? Because the plant is consuming the nutrients, and you'll have softer and more delicious buds. Enjoy your grow and keep up with the flowering nutrients you're applying!

Without a diary is hard to pinpoint this could be a lack of nitrogen or a problem with your PH 6-7 for soil, Over- or under-watering, and also temperature can play in a roll of yellow old leaves you need to know but I will say PH or lack Nitrogen from the pic

I'm in week 6 out of 9 +- Forbidden runtz auto..

I do not know exactly which week you are but is normal for old leave to turn yellow and die because buds eat from the leaves in flowering

A cannabis nitrogen deficiency will cause the older, lower leaves on your plant to turn yellow, wilt away and eventually die. The plant typically appears pale or lime-colored. The yellow leaves of a nitrogen deficiency may show signs of brown, and they will usually become soft and sort of “fold” in, before possibly turning crispy but ultimately falling off on their own. Sometimes you can get the signs of a cannabis nitrogen deficiency if the pH at the plant root zone is too low, even if the nitrogen is there. This is because when the pH at the roots is not right, your plant roots can’t properly absorb nutrients.