Are You Giving Your Dracaena Sun or Shade?

Dracaena Sun or Shade

I am craving for your advice. I have my Dracaena Tricolour for 6 months. In the shop they said this plant needed some shade. I put it in a deep niche we have near the window. I water it once weekly and wash the leaves once in a fortnight.
Lately my dracaena started losing its leaves, and some small brown dots appeared near the trunk. I am not sure, is it more correct to give my dracaena sun or shade? Or maybe the reason of this condition is something absolutely different?

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I know that dracaena propagation can be done by either cutting off its top or by pulling out seeds from dracaena fruit. I plan to have some more dracaenas in the future. But if I don’t overcome these dots, I have concerns of losing this plant for good!

Some forums say dracaenas like diffused light. But the lighting in that niche is diffused indeed! I was thinking if the dots could appear due to dryness of the soil. But I check the soil regularly, and I think I water enough. I fear to dig the plant out without a real need.