Curry Leaf Yellowing

Hi All,

i was hoping that someone might be able to help with a curry leaf plant we were given. It's a Murraya koenigii curry leaf tree and was lush and green when we got it in September. It's starting to gradually yellow on some of its leaves. I've fed and watered it but the yellowing continues. It's indoors, on the front room on a sunny window. can anyone help? Does it need a different nutrient or is it just natural l in the winter?

thanks