Northern lights with yellowing leaves

Thank you all for you comments. It seems that it was a mixture of things. Excess water from the flush was clearly something and I think low temperature was another factor. I did a number of things. First I gave her some more nutrients, but that didn't do nothing. Then I took the plant out of the pot, the root system is really developed, and put some more substrate on the bottom of the pot and on top. After that i gave her some more top max from biobizz mixed with crushed snails and a small teaspoon of ash, I did that in case there was a calcium issue, don't really know if it's efficient or not. The result was that a day later the leaves are back up and the buds are growing again. Gonna keep monitoring the next days and update with pictures on monday maybe.

Hey m8, Are sure temps didn't dropped below 17C° or you didn't watered with cold solution?! Cold temps in soil can cause deficiencies and drooping leaves.

i see over watered and under feeding earlier let them dry out before re watering, don't go the other way and over feed now cos there coming to the end of food in a couple of weeks and will draw from the leaf, hence yellowing clue is in what you said did a small flush and things got worse your substrate is wet can see that in pic let it dry an they will buck up

What kind of lights are you running and at what distance?? Seeing as you eliminated other factors my next best guess by what I’m seeing is some sort of heat stress! Put a thermometer right next to the canopy and see if you can lower that if it’s high! Raising your light? Better airflow??