The dark inner leafs with the slight tip burn random brown spots looks like phosphorus deficiency to me
Could be caused by
A lack of (p) in the medium
An Improper ph
(5.8-6.5) hydro
(6.0-7.0) soil
Over fertilisation
Excessive levels of other nutrients, such as zinc and iron, can interfere with phosphorus uptake so revise your entire feeding schedule to see if you have multiple supplements and additives that do the same job.
Low temps can aslo interfere with the uptake of (p)
A couple ways to fix (p) issues is
Monitor temps
Ensure that the temperature conditions are between 70-85°F (21-29°C) during the day when the lights are on. It can be slightly cooler at night but don’t allow for large temperature swings
Monitor your ph
(5.8-6.5) hydro
(6.0-7.0) soil
Increase the phosphorus levels in the growing medium by applying a high-phosphorus fertilizer.
As a last resort you may need to flush the growing medium completely with clean pH water to remove excess nutrients and reapply a balanced nutrient solution
Hope this helps