Help needed!

Heys guys i have a probelm with my fglowering plants. I have two white widow and 2 ice cream in flower, the girls are about half way to harvest and they are looking fine, but on the lower branches the leaves are looking bad. The new growth on said branches are turning yellow form the inner side to the tip and i have no idea why.
The plant otherwise look healthy. I have my temps between 18C - 27C rh 45-65%, fert: plagron alga bloom 5ml/l + pk 13/14 1ml/l, they are getting about 2-2,5l/d and are in 15l air-pots.

Plese guys atleast share your ideas about this, i really dont have any, this is my 2nd run but nothing similiar before and im really afraid for my plants. Please help me.

did your plant get cold recently?
Can you take some closer Photos?

Hey, thanks for your attention, i made a few more pictures.
I dont think temp is an issue, but i just cheked the lowest temp in the tent was 15,6C. The plants upper section looks absolutley fine, only these lower branches producingthe problem, and on the ice creams the yellowish leaves look like the tips are rotting and eventually drying off.
The pics are from 1 of the ice creams but the other are similiar.

the upper section looks healthy:
View attachment 2847058View attachment 2847059View attachment 2847061

the lower not so much:
View attachment 2847062View attachment 2847064View attachment 2847066View attachment 2847067View attachment 2847069View attachment 2847070View attachment 2847071View attachment 2847073View attachment 2847074

i see dry space in your pot. And wet space. That means you aren't evenly watering the medium. Pound at least the volume of water of the pot through it at half strength nutes, check the runoff before and after and you'll be surprised. My guess you got salt buildups my man.

EDIT: Check the runoff for TDS, not for pH. Make sure it's 5.8 going in.

Thx for your answer. I'll flush em tomorrow with twice as much water as the pot.
Im constantly monitoring the ph off the water and the runoff, and its in the normal range if im correct last time the runoff was about 6,7. i dont have an ec meter sadly but i'll manage to get one by the end of the next weak

how many weeks into flower? it looks like 3 or so with like 5 or 6 to go.

its about 4 weeks im expecting to harvest at the end of october/1st week of november. the 2 widows look more advanced than the 2 ice.




Could the yellowing be from these branches not gettinjg enogh light? coz my box is more than full and on another forum a guy said it is because of that. I thought about it before but not sure of it.