New grower help!!

This is a 30 day old og kush auto. Found brown spots on a couple leaves. Indoor, soil, fox farm grow big, big bloom for veg tiger bloom for flower. Ph is always around 6.5 when I mix. Checked runoff the other day 6.3. This is new to me. Is it nute burn, light too close 18” , I thought potassium deficiency one guy said don’t worry too much about it it looks fine possibly pushing nutes to the max. Thanks in advance
 

Attachments

Top