I've heard some things about overvegging yes but won't happen to a plant thats been in veg for 12 weeks.I know people vegging for at least 5 months with no problem.You only have to control its height and overall growth.
as long as you don't have serious nutrient problems, soil problems like ph and bugs you don't need to worry.Unless problem is really serious,it won't cause any flop in yield and quality.We all have small nutrient excess , some pests , and temporary ph problems , if you can handle it well as you seem to be doing so,everything will be fine.You can just consider doing a simple flush to get rid of nute excess,your tips looking a little bit burnt.nothing serious in there,looking fine