Problem with overfertilization or potassium deficiency or something else? 3 weeks

Greetings my grower friends
This is my first post since my autoflowering Orion F1 gift from RQS has forced me to ask around here what is happening to it, it worries me.
It is in a white pot with universal healthy compo substrate mixed with perlite and worm humus.
A little over a week ago I had to go on a trip for 5 days and when I returned on Monday, I found the plant like this:

Before I left, I watered it abundantly (I think the first mistake, since when I returned it was still very humid), with homemade lentil rooting agent in a low proportion mixed with filtered and distilled water. pH around 7 and EC about 0.8. I left it inside the house next to a window where it is bright all day and the sun shines on it in the afternoon for about 3 hours (in the place where it is usually it receives more light, but it is also more unpredictable and quite hot, I live in Spain ).
I thought that the damaged tips might be due to the long wet time, so I waited, but the damaged tips continued to progress and appear on the other leaves. Yesterday I was pretty sure it was due to overfertilization, or so my beginning eye thought. So I wanted to clean up the substrate a bit: I removed the top layer of soil that was hard and crusty, added new substrate and watered with very weak 0.04 EC mineral water.
I thought it would improve, but today I found it like this:

I have used an app for images of diseases and what I find most similar is a Potassium deficiency, either due to a shortage, incorrect pH or, according to him, excess calcium and magnesium.
What do you think? What should I do with her? My hope is to solve the problem and that the new shoots continue well and take the plant forward, although being autoflowering it will give very little, but I am fond of it.

It looks like it has too much water

Hi @Robbob04, Welcome to the Community!

I think there are 2 issues that hurt the plant.

1. Over-watering/Keeping the soil too wet/Not letting the soil dry out.

   • At the early stages, the seedlings take in moisture from the air, via the leaves, so a high Relative Humidity (RH) is required, and
   • If the soil is too wet, all the time, the seedling will drown.

2. The yellowing and crispiness of the leaves, to me, is nutrient burn (over fertilization).

I would suggest that you start over, and prepare a growing medium with less fertilizer/nutrients in it. Also make sure the growing medium has Good Drainage, and water retention (50% Peat moss or Soil + 50% Pelite or Vermiculite)

Thank you very much for your answer @Rasta_Free-Man, also to you @Bob62 .

I think you are both right. Until I had to go away for a few days, I watered a little more than once a week and everything was going well, but I overestimated the amount of water they would need in my absence and overwatered. And a few days after coming back and seeing signs of overfertilization (I thought it was due to the rooting), I wanted to wash the substrate a little, so the roots have been able to breathe a little.

The one in the photo is officially dead. Its shoots didn’t grow anymore and started to turn brown. I have already thrown away the soil from which many dark-winged fungus gnats have grown. I imagine that from the high humidity. I also germinated and sowed a new seed. I hope I don’t upset her this time. The culture medium is about 60% universal substrate Compo Sana, 10% earthworm humus and about 30% perlite than the previous time. I think it will go better if I calculate your water needs better.

I have 2 questions:
1- With regard to maintaining humidity, I don’t know how I could achieve it, since I don’t have a closet. My intention was to have them on the balcony. The relative humidity where I live ranges from 40% to 80%. Sometimes less. It would be good? If more is needed, any advice to improve it without a closet? Also the temperatures that we reach outside are up to 36º. Better to keep them indoors for now and later they will be able to withstand better?
2- Is it possible to burn for fertilizer only with vermicompost? I understood that it was safe.

Thank you very much for your wise words

Place a clear plastic dome over top of the plant. You can make one when it is small. Just get a clear solo cup, poke holes in the bottom for some air to exchange, tape it upside down, on top of the solo cup that the plant is in. I can also buy clear domes for this purpose.

I think for seedlings, any compost/nutrients is too much, the seedling has all the nutrients it needs for the first few weeks, so no fertilizer/nutrients in the early stages is safest.

Don’t mean to contradict you brother but I would not recommend this in Spain - it’s gonna be 102F in Malaga today lol. The lensing and greenhouse effects will kill her in minutes. It would be fine while inside, just don’t use them outside.

Best thing to do is spray the plants after sundown with a refreshing foliar feed, ideally with an anti-stress ingredient like aloe or something. Otherwise there is not much you can do about humidity outdoors, it just is what it is.

Keep her out of intense maximum sun, protect from wind and rain, keep the soil light and airy and on the dryer side. Watch out for bugs, and consider an electrocultore antenna too to help protect from stresses.

Thank you for jumping in on that @SJ1! And no sorry necessary. I forgot he was outside (was thinking of a different thread) sorry @Robbob04 , please refer to SJ1 guidance above