Is it on all fan leaves?
Might need some cal- mag.
Look at the back side of the leaves might have a pest.
Looks like the culprit. Hope this helps
@Hashtonbutcher good looking out Growmie
I agree. Check for pests, and a few more pictures of a few more leaves would be helpful.
Wouldn’t there be pest waste( ) or eggs left behind with that much damage. You definitely know more than me so please teach Sensei
Not always. But you will see activity of feeding on the leaves. It’s much easier to spot. Pest waste is so small, you would almost need a microscope to find it.
So in short it’s much easier to see something moving, or from where they ate part of the plant.
The above picture looks similar to a thrips problem. I’ve had them, and their easier to rid than spider mites, but neither are desirable to have.
I circled an actual thrip on a leaf of a picture stolen from the internet. Thrips “usually” hang out near the veins of leaves, undersides, and the crooks of where the leaves near the stems.