Having some issues in early flowering

[Horus]

First of all hello everybody!! Happy new year!!
My best wishes to the community!!
I'm coming here to learn how to grow weed easy😊✌️
I'm not a new grower but i still have a lot to learn.

Let me start with a problem i facing for a third grow in a row.
Long story short, for the third time I having same problem in early flowering. This time not as big as previously. Plants are regulars and i vegged them for around 50 days.
Problem starts after one week in flowering, in the middle of stretching phase.
Veg was perfect, i used some local potting soil and Trabe Nutrihemp (npk 7.4.6. +2.mg) and GuanoKalong bat guano (npk 1.10.1.) as soil amendments right after transplant of the seedlings. Both are slow release fertilizers. BTW exactly same combo were used on some lemon Autoflowers and they ended up sweet.
A little bit later I noticed that GK bat guano is actually a flowering fertilizer.
Anyway, when problem showed up, i used some greenhouse power feeding (my water is always at 6-6.3 PH), few days later i added some liquid PK 14.23 slow release fertilizer, and furthermore some iron and a little bit nitrogen. Looks like plants are recovering but a little stunned.
All i can guess is that the nutrients were depleted until the the first week of flowering and plants were extremely hungry. Im still not sure what exactly was missing.
The problem started as chlorosis and yellowing of middle and upper fan leafs, some even turned crunchy. Bottom leafs stayed perfectly fine.
If you guys have any ideas on what's missing or need any more info, im right here.
I hope my photos can tell you what's happening.
Thank you for your time and stopping by!!

[crucialbunny]

This type of problem seems to be relatively common for growers using slow release nutrients in their soil. Plants will often do wonderfully while in veg because of all the nitrogen availability. However, as soon as flower begins, they start to fade. At the onset of flower, a cannabis plant's nutrient needs change like the flip of a switch and P&K become the vital nutrients to carry on the growth process. Excess nitrogen in the soil then disrupts the ability of the plant to absorb other needed nutrients in what is often referred to as lock-out. Many beginning growers will see their plants starting to struggle and the gut reaction is to think that the plants have exhausted their nutrients, so they start adding more of what the plants were thriving on during veg, compounding problems. I see in your photos what look like a number of sacrificial leaves where the plants might be trying to rid themselves of some of the toxicity. Maybe a couple good flushings might help?

[SoOrbudgal]

I think crucialbunny is spot on for correcting this. Hold back the ferts and give that soil plain water let alittle runoff then allow to dry , plain water on the 2nd needed drink and just go easy with the flowering fert. Your gonna loose some leaf now no more will grow so make sure not to over water or add slow release with N in it just PK. My bloom has less than 5% N just saying

[3Berries]

I think during 12/12 stretch that should be considered veg as far as feeding.

[3Berries]

I've always seem to have potassium issues after the stretch. In the past it was the old pH lockout issues from too much veg nutes. The last two times around pH isn't the issue. So I looked at my nutes, MG bloom booster 15-30-15 and see it's a bit down on potash compared to other brands. Last grow I added wood ash during mid and late flower but it's too late by then it seems. I have some MasterBlend 4-18-38 nutes that has a much better P-K profile. Going to use it for flower next grow.

[OldManGrower]

Well I kind of agree with the above, but the leaf markings show PH issues. First, I would flush with plain water and cal-mag. Check your PH, I have found that I have similar issues anytime my PH gets below 6.4. Add a double dose of cal-mag to water after the flush.