Leaf yellowin during late flowering

Ey, so i recently got a problem with my fan leaves turning completely yellow and dying during my 7th week of flower of these 2 plants sativa dominant Amnesia Kush...
The strange thing is that the leaves dying are from the top canopy not the bottom ones; here you can see som yellow leaves here and there on the top canopy



These are 2 plants under scrog, the right plant has always been more green/yellow, while the left one always dark green since seedling







I've been feeding them with Plagron nutes (Alga bloom+Green sensation), keepin my ppm to 1050, lowered recently to 900...
I'm currently using my tap water (250ppm) instead of RO water, could it be the chlorine in my tap water causing this?

The pots are 26L and i'm feedin them with 4,5L (per plant) every 2 days...
Maybe the pot is oversaturated with nutes,meaning i need to flush them more often...
Ph is always near 6,5

Also i have to mention that only 2 weeks back i was able to create a drain system to allow the pots to be completely flushed.
So before that water didn't drain out of the underpots flushing and cleaning the leftover nutes.

This is the "system" to allow drainage (basically a table with holes with a container under it to allow me to remove the water in excess)




so Right now every time i feed/water, the solution flushes completely the pot, releasing water from the underpot.
So maybe this problem is related to my early mistake of not flushing them, and these are the effects of old nutes that stayed in the pot for too long...

Bump anyone?

Yellowing of fans from the bottom up (if that is the case) would indicate the plant is using the mobile nitrogen stored in those leaves to form buds. If this is happening too early for your liking (you want this in late flower) then it indicates you should run nitrogen a little higher in early flower (next time) with this strain. Any addition of nitrogen now should be brief as we don't want too much when they are ripe. If the nitrogen is lowered too early then yields will suffer. I like to keep running a veg feed during stretch and then switch to a bloom feed.

Renfro said:

Yellowing of fans from the bottom up (if that is the case) would indicate the plant is using the mobile nitrogen stored in those leaves to form buds. If this is happening too early for your liking (you want this in late flower) then it indicates you should run nitrogen a little higher in early flower (next time) with this strain. Any addition of nitrogen now should be brief as we don't want too much when they are ripe. If the nitrogen is lowered too early then yields will suffer. I like to keep running a veg feed during stretch and then switch to a bloom feed.

Click to expand...

Ye i continued the veg feed till the end stretch too.
But the leaves are yellowing in the top canopy here and there look at the pictures, they're not the bottom ones....
For some reason the bottom ones are full green, but some on the top are yellowing any idea?

Dr. Frescho said:

Ye i continued the veg feed till the end stretch too.
But the leaves are yellowing in the top canopy here and there look at the pictures, they're not the bottom ones....
For some reason the bottom ones are full green, but some on the top are yellowing any idea?

Click to expand...

If it's not from the bottom up then it's not the nitrogen.

I am curious what the pH of the medium is.

When in later flower a potassium deficiency can sometimes present itself like this. Do you know what the elemental PPM of potassium is in your feed? Too much magnesium can lockout potassium also. Just something to look at.

Renfro said:

If it's not from the bottom up then it's not the nitrogen.

I am curious what the pH of the medium is.

When in later flower a potassium deficiency can sometimes present itself like this. Do you know what the elemental PPM of potassium is in your feed? Too much magnesium can lockout potassium also. Just something to look at.

Click to expand...

the medium is 6,5 in ph

i used to add calmag solution every feed, that was a mistake cause the solution i added was not intended for every feed use, but to correct deficits...
Can't really tell what's the exact PPM for potassium, guess i'll just have to add more green sensation if that's the problem