dracaena marginata tricolor leaf problem
I have a nice 6 foot tall dracaena marginata tricolor in my living room. I've had it for well over a year in the same spot with no issues other than some mealy bugs. I have recently been observing white bands form on the top two heads of the tree. The bands have no color and the leaf is slightly deformed in the area. First there was one on one head, then two, then a second head got it. On the second head, the whole growing bud thing is deformed at the whitened area.
Does anyone know why these bands are forming? What can I do? They seem to be spreading!
Some additional info if it matters: Plant is in a bright day lit room and receives a little bit of direct sunlight during summer. soil pH: 6-6.5. Watered once a week. Room temp varies 65-85. Rest of the plant looks perfectly healthy.