The disappearance of the green/yellow/red root growth tips simply means they are not actively growing.That could be a case of the plant “taking a rest”, or it could indicate a minor cultural issue.
Lack of humidity is not likely the problem down there. Do you have any info on your water quality or municipal treatment. Have you been feeding it at all? If so, what formula, how much do you mix per gallon, and how often have you been applying it?