Disease ID

pugslovesun

hi , hoping someone can help my friend by letting us know what’s going on

pansyface

leaf miners
larvae of some flying insect or other.
tear the leaf off, split it between the upper and lower layers (remarkably easy to do) and you will find the little blighter. Perhaps this one.
https://www.naturespot.org.uk/species/scaptomyza-flava

pugslovesun

Ah many thanks, will pass this on to her.