what’s wrong with our golden pothos?

Context: we are renting short term from a houseplant lover who asked us to water their plants on a weekly basis until our lease is over.

The first image is how their golden pothos was at the beginning in October, very lush and healthy.

However, now as you can see in the second and third photo, the leaves are very wilted and have been falling off the plant and some have been turning black, leaving the vines almost bare for the past couple of months.

When the plant started deteriorating, we thought we were overwatering it and switched to watering it every 3 weeks instead of weekly.

To clarify, the plant started behaving like this when we were watering weekly AND continues to do this now even though we are watering every 3 weeks.

Can anyone please diagnose this issue and tell us how to fix it?

TIA!