Still quite a few issues on the fan leaves. I finally bought a pH meter and the pH was too high so I lowered it to about 6,5 and it's back at around 7 now which should be fine. The problem persists so it's likely still septoria. Will give my environment a proper cleaning before my next grow but air circulation is good and humidity low so there's not much else I can do for this grow.
@heizen, thank you but this grow actually completely went downhill after this point. What I thought was disease was more likely pH issues as my meter was giving wrong readings. I've started a new grow where I kept a flowering clone of this plant tho :)