Hi sound like an over application of paper adhesive and you have un knowly strecthed the paper when you hung it. Options are to hang it again or try and match a decorators crayon to the colour of the paper and colour in the white lines if you can live with that.If your colouring in the lines try it on a hidden bit of the wall first to check the match. The white lines could even be the edges of the paper showing, this is normally the case on dark coloured paper. Hope this helps.
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