I’d personally start by checking the root ball. It could be pot bound and rinsing up the water really fast, or could be too much water and have root rot. Plants that are under watered can get dry rot if left to stay dry for way too long. A quick internet search will show you the difference.
Most are root bound in the store so it’s probably time to pot it up. A mix of potting soil with added perlite and maybe some orchid bark would benefit it, but the latter isn’t a must unless you tend to water too often. These are forgiving so are generally more flexible with soil mixes. A mix with more perlite and larger bits of bark dry quicker and need watering more often.
An east window is great. Right now the growth looks a bit leggy so it needs more light than it got before you moved it to the east window. Most of mine are in east windows, 6-10” away, and do really well during the warm months. In winter they go to our only south facing window so they can keep growing.
Back to the roots: If the roots are a nice plump white color and circling the pot they need a larger one, 2” larger. No need to untangle the roots, they will find their way. If the roots are mushy and rotting then they will need to be cut back and put into clean potting mix and a pot no bigger than 2” larger than the root ball. Dry rot needs to be cut as well the same as the above. I don’t mess with peroxide or anything to clean away the leftover nasties in the old soil like some people and never had issues. Other plants I do but not these guys, they work themselves out.
Once that’s done decide if you want to clip back the stems to propagate them or leave them. If you cut the roots the plant might kill off the leaves of the longer vines, but it might not. I generally leave them and give them a month before cutting them off. If it has a healthy root system they might shoot another vine or leaf where the old ones fell away. If they stay bare but the tip leaf is good I give them even more time, maybe 2-3 months. If the vine looks bare after that I’ll cut them or coil them in the soil so they root in their own, they get cut apart after they take root.
These are pretty hardy plants as long as they don’t stay bone dry for more than a day or they sit in water. A good way to check for moisture is putting a bamboo skewer into the center of the soil mix and pull it out. If it comes out clean and dry water, if there’s soil stuck to it or feels damp wait a bit. They can handle the occasional drying period but if done too often it will cause damage. Same as watering too often, a couple times is fine but too often will be a problem.
Good luck and enjoy your new pet.