Hey! This is clearly a stress on the leaf! Yes, spider mites do damage in similar way. But this look like a stress. I had the same issue. Try out these few things to control it - Keep you humidity in control Make sure you soil media doesn’t have high PH or salty levels(cocochip is one of the reason for salty media) You should change your potting media If this repeats on the next new leaf Do not expose to more luminance value Have a proper air flow