I have two ZZ plants and while they each are putting out new healthy stems, I'm losing others when the leaves turn yellow. From what I've researched, I find conflicting information about watering practices. Some say they need little water so I have held off watering for a few weeks but that didn't save my original ZZ plant. I have had these two ZZ plants for a few years and they were doing fine but then some of the leaves started yellowing. I limit watering to every 2 weeks and I only water the top inch. But some of the stems' leaves continue to yellow. The plants already came with fertilizer beads in the soil and the pots have an attached container at the bottom for drainage. They are placed in a window with indirect sunlight. These plants are supposed to be low maintenance but I'm clearly doing something wrong...

Thanks in advance for any advice!