Never seen this before any ideas?

this is happening to my oldest plant the leaves are very soft and wrinkly idk how to explain it so here's some pics

temps stay between 70-76 humidity is low right now around 20%

i have 3 other girls in there with her and it's only happening to her they are all cut from the same mother

Could be a nute/salt burn, flush then see how it is. Not a major issue.

new growth looking healthy after a flush and redose of 1/4 strength nutes

don't know what the flush did because I don't use any media or top feed or anything but it worked! lol