In my opinion nothing ๐
I often see this with my lower leaves because they sometimes touch the wet soil or get wet when Iโm watering my girls in a rush ๐คทโโ๏ธ
Overal your girls look pretty healthy to me
Just keep a good eye on the damage and in a few weeks youโre probably gonna pull that leaf anyway so no worries
Happy growing and keep them strong ๐ช๐ปโ๏ธ