yellow leaves

Hello Friends. I got these outdoor sativas here that just started to flower a month ago but now suddenly some of the leaves are turning yellow. I use slow release fertilizer that lasts for 8 months. The ph of the water is exactly 6.5. Also, some plants are more affected than others. I know it looks like a nutrient burn but then all plants should be equally affected which is not the case. Besides up till recently everything looked perfect.
Could it be some fungi or mold? I don't see any bugs in this garden..

Hey, I did read all the posts first. Im not just posting without doing my homework. To me this looks like they are out of nutrients. They re starting to feed off the bottom leaves and I heard that the slow release fertilizer don't last as long when its hot. So that would make sense. Should I just try feeding them additional fertilizer? here is a pic of some more leaves I picked off this morning:

Can anyone give some some advice please?

Your big fan leafs will yellow starting at the bottom working up, they will die that way to.
Some strain they go yellow sooner than others. Your Other leaves should be healthy nice green.
Top middle plant looks like a Mag. Def. get some Cal/Mag, Even if your plants don't need it I give mine 1 dose per month as a preventative.
I wouldn't use the slow release ferts. Get something fast acting for the next grow.

Good Luck with your Grow.

Thank you so much for your answer. It helps a lot to have another opinion. I'll get some Cal/Mag and see how that works out.
Why do you advice against slow release fertilizers? They worked great up to this point. Just curious...

oetzi said:

Thank you so much for your answer. It helps a lot to have another opinion. I'll get some Cal/Mag and see how that works out.
Why do you advice against slow release fertilizers? They worked great up to this point. Just curious...

Click to expand...

There harder to get out of the soil before harvest. You want to get rid of nutrients in the soil before harvest.
I water the last couple of weeks before harvest. Basically flushing the soil over time.
Or you can do a one time flush, for ever gallon of soil 3 gallons of water before harvesting.

If your using organic nutrients you don't need to worry about flushing.

I agree - make the switch to organics over slow release. Also - the leaves will yellow through the flower process as the plant focuses more on phosphorus uptake than nitrogen. Calcium and Magnesium are good. Also neem oil helps prevent deficiencies and gives the leaves essential oils to keep them healthier/problem free. Good luck on the grow.

txs you guys. That helped a lot to clarify things. I got a month or two to go still on some of those ladies...
I only used slow release cause I was on a budget. Next round I'll try something else.
If ya don't hear from me it all went well

Hi friends
I agree with all of you . When i started i also faced the same problems but soon i found lack of chlorophyll is the main reason. As well as nitrogen controls the proteins so nutrient element may also be responsible for this .