I have a Yucca Cane plant approx 36" tall and is in a 10" pot. This is my first winter for it and have brought it into the house (temp 66-69)and in a bright room. Recently the fronds have started yellowing. Could the pot be too small now or do they do this over winter? There are new fronds still growing from the centers but are not as deep green color. Any help would be appreciated.