small white lines on leaves

[Runzamuk]

Hi ... I have these small white lines on some leaves. I dont think they really look like leaf miners or Thrips, or White powdery mildew. Am i wrong, or is it possibly something else?

[Runzamuk]

under 100 magnification the lines look granular.

[crucialbunny]

Notice how it is built up in the vein indentations and is more pronounced toward the bottom of the leaf? This makes me think that it is calcium from water that has dried there. Have you tried wiping it off?