Planted Tank Obsessed
Join Date: Jan 2019
Location: Montreal, Quebec
Welcome to TPT.
For better advice it would be helpful to provide all details of your tank to get the best diagnosis possible. I see several unhealthy plants in that picture not just S. Repens.
A Full Tank Shot, your CO2 levels(ideally pH at lights on and off), Your Weekly fertilizer dosing in ppm of all Macros and your Micro Dosing.