Welcome to the forum!
There is most likely a problem with the plant's roots.
Can you share some more information with us? I see that it is double potted.
What sort of soil is it in?
How do you water?
How often do you water?
Also, did you follow the anti-gnat pot topper instructions to remove 1/2 inch of soil before adding the product?
It is normal for it to take on the brown/tan coloring of the underlying soil, that is not the problem.
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