Potassium

So when i first purchased the plant i had mentioned that i thought that Nanners was potassium deficient. For a while she looked great, and i give the credit to the special blue water (miracle grow). Now however, i noticed a little bit of brown spots on the plant again. I wonder if this is from when i didn't use the spesh. blue water. I hope it goes away and it is healthy again soon since i am using the blue water again.