Problem with a tree

[MarcAnt]

Hi,

I just started sowing my first seeds this year. Most are doing very well, but I have a problem with an adansonia digitata (baobab). At first he looked very healthy, but since some time, leafs are turning very light, the green color disappears and they finally fall off.

This is the complete plant (almost 2 months):

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As you can see, the top leaf has already started developing the problem: two small white marks at the left side, it looks like something caused by an insect, but I can't find any such beast in the environment that can cause this (only some flies).

A detail of the top leaf (but not very sharp, I don't have a macro lens)):

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I don't know if it is still possible to save this tree, but information about the cause and eventually how to prevent it in the future, will be very welcome.

Note that I have this tree inside. Outside, it would surely be too cold for him in winter and probably even late summer.

Thank you in advance for any suggestion, Marc

[Toni]

Are you feeding?

[MarcAnt]

In fact I do, although it's possible that I don't feed enough, I probably kept it too long in the original soil (for seeds and seedlings). I also gave a slowly releasing tablet (sorry, english is not my native language, I'm trying to translate), but that might be too slow. Last week I moved it to compost which, according to the package, already contains food.