Nutrient lockout - how to proceed after flush?

[pusa]

Hi everyone!
Not new to growing completely, but it is my first time indoor operation.
I am growing few Pineapple Express autoflowers from Fast Buds. Girls are planted in BioNova Bio SoilMix. They are started now their ~ 8th week. I was feeding them with BioBizz products: Bio-Grow, Bio-Bloom, Top-Max, Bio-Heaven with little bit less than half of recommended doses (https://www.biobizz.com/wp-content/uploads/2020/03/Nutrient-Schedule-EN-2020.pdf). Around 6th week I noticed some cal-mag deficiencies (tought PH was to little bit to low when watering), so I started giving them CalMag from same company for every watering... but lately I realised that it is advised (look at the top of the nut schedule pdf) to put CalMag only once a week and I was putting deficiency recommended amounts for every watering *facepalm*.

Plants were doing more or less ok so at the end of 7th week I decided to give them full of recommended dose and all the burn/lockout happened that you can see on the pictures - purple leaves, tips burn, yellowing and some leaves are very pointy (upwards). So 1-2 days after I performed a flush (5l of water through every 5l pot) - no nutrient feeding afterwards. It was 2-3 days ago.

Yesterday I bought EC meter, poured some water trough 2 plants again (in order to have some runout to measure) and the value was very low I guess (0.3-0.4). Soil is still wet in all of plants and I am confused what to do next. It still needs at least 2-4 weeks to harvest. Any advise how to proceed with them now? I water now with 6.5 PH, but to be honest I don't have an experience with measuring EC.
Thanks!

 

[greenfingered_guerilla]

I feel your pain!
I've been using the full Biobizz range on my photos with outstanding results for the last year but now I'm running an auto-crop for the first time and growing these I've run into the same problem.
I doubt I'll be able to save the plants that are affected the most but fortunately I've 8 more lesser affected plants to focus on that are now in full flower.
I would have thought that Biobizz being such a huge company would have clearly draw up a designated Autoflower feeding schedule for auto-virgins such as myself.
I've also found out that autos will do better off growing in Biobizz Light-mix rather than the All-mix as theyre not as greedy as photos.
I flushed mine (they're in 12L fabric pots) with 25L of ph'd water each then let them almost totally dry out for 5 days
The next feed they recieved 2L ph'd at 6.5 each of 4ml/L of Algamic & 1ml/L Activera only & 0.5ml/L Calmag
It took almost 2 weeks to see signs of the chlorophyll returning to their weird bleached avocado yellow leaves.
Brutal, I feel like a bad parent!
I too shall be purchasing an EC/TDS meter. Apera is a reliable brand for these and reasonably priced too.
I use their ph meter that you can find on Amazon.
All the best with your ladies

 

[pusa]

@greenfingered_guerilla Thanks for sharing
I have Algamic too. I guess I will let them dry and then proceed with Alg-A-Mic & CalMag from next watering, maybe give like 1/4-1/5 nut doses afterwards. I'am just wondering if low EC (recommended for flowering autos is around 2 I think) might somehow be destructive in my case and I should level it up, but I feel like what's best for them now is some "rest" and maybe they will manage till the crop. Btw. I still observe that even with most affected plants, buds getting fatter every day . All the best man!