What’s wrong with my rhaphidophora tetrasperma?

The top is growing well, but bottom leaves are yellowing and keep dying one after another.

• No root rot, but the roots are very small (less than a handful of them);
• The plant is about 2 years old, repotted in soil/perlite/orchid bark mix 3-4 months ago, has been fertilized once recently;
• Temperature at home has recently gotten a bit lower, about 18-19 C;
• Bottom leaf damage is irrelevant (I have a cat).