Yellowing of leaves top growth

Have noticed these yellow marks on 2 or 3 leaves in the last week.marks seem to be from the centre of the leaf,right on the vein.heat and humidity night 25degrees/50% humidity.dsrk period 21 d/55%.grown in a 5 gallon pot,feeding her half nutes of organic biobizz once a week,grown in organic soil also.its the 8th week from seed and heading into 4th week of flower.strain is northern lights.i water 2.5 ltrs every 2 days.feed,molasses water,ph water,this is my schedule,plant is still growing but have no idea what this is coming up on the leafs

Are you on a watering schedule, is the soil still wet when you water? The main issue, I think the yellow spots are chemical burn...

Watering schedule is 2.5ltrs every 2 days.so say monday nute feed wednesday molasses water friday ph water and so on.i allow the pot to dry out completely between the watering.i was feeding 4 ltrs ever 3 days but felt i may have being overwatering so decided to do less.nutrients are all organic so there should be no salt buildups or any reason to flush.i ph the water at 6.5 every feeding and runoff reads about 6.8.you say chemical burn,is this the same as nutrient burn?there is no yellowing of tips or leaves on the lower part of the plant at all

Same thing, its when the roots are not able to take in all the nutrients because its being overloaded. Think of it like a washing machine, putting more than directed soap amount may seem like a good idea but it won't wash your clothes because there's too much. It just can't absorb all of that (organic or not). Feedings should be once a week. I Wouldn't just water because its been two days. Water is the number one crop killer

So how would i approach it now to help the plant?

It could be just that fan or not, but I would definitely change its possition...