Hey I don't know what's happening with your plant but perhaps someone with more experience can say. Please also show the underside of the leaf. From the top I am suspicious of bugs. If you see any raised dots on the underside, that would confirm bugs. It can't hurt to spray with some (about 1-2l) water with 1/2 tsp each of soap like Dr Bronners and neem oil if you have it. Keep us posted.
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