White Stuff on Arrowhead Plant Leaves?

I have this huge Arrowhead plant. It's growing beautifully and very full. However I've been noticing this white stuff around the edges of a lot of the leaves. It stays right around the edges of the leaves. I've tried washing it off but it comes back. Can anyone tell me what it is and how I can get rid of it?

Hardiness Zone: 7b

By Cricket from Parkton, NC