First a little backstory: I bought the basil at a supermarket, where it came in a small plastic vase. I kept it in this vase for three weeks. During these three weeks, I did the following:
- kept it at the window, with an additional timer lamp to provide more light during the evening (here the sun goes down very early)
- watered from the bottom, with a reversed coke to always keep some water around. The result was a humid soil on the top.
- on top of a heat radiator. There's a space of 15 cm between the radiator and the actual board where the vase is sitting. I am not using an aggressive temperature.
In these conditions, the basil appeared to grow well. Got good leaves and new sprouting leaves were well established. I got a couple of slightly yellow leaves in the lower parts of some plants. This may hint at excessive watering, as I read around.
Two days ago I realized the roots were coming out the drain holes, so I decided to transplant the plants into three vases. It is the first time I attempt this procedure, so I am quite sure I did it wrong: I took the plants out of the old vase. I found out that it was basically a lump of roots. I tried to pull, and I clearly felt the roots breaking. I tried to put the lump in water to release some soil but it remained a (now wet) lump. Ok. I just pulled it into three pieces, moved each of them into a vase, where I put some new soil, the lump, and soil all around and to cover it. The new soil is pH 5-6.5, with NPK 14-16-18 fertilizer in slow release coated granules.
After the transplant (which I did at around 15:00, which means that after the transplant, the plants got only three hours of indirect light), I put the three vases (which have drainage as well) in basically the previous situation: a water buffer in a larger container, with the vases inside. The only difference is that I haven't provided artificial light, since I am using the lamp for some sprouts.
After only one day, some plants are clearly stressed and on the brink of death.
This is one of the three vases. Note how some plants appear healthy, while one is clearly dying. This happened within 24 hours.
What did I do wrong ?