Hi, we've had our Zz plant for 4.5 years and it just star...

6ft to light, indirect

6β pot without drainage

Last watered 4 weeks ago
I suspect they may not be mealybugs. Mealybugs will leave white fuzzy patches. No fuzzy patches no mealies.
With zz plants their older foliage can get white spots. The reason behind these βspotsβ is over time when watering your plant, the leaves can excrete some of the minerals that are absorbed through their leaves. They will show up on older leaves as white spots. This may be the case with yours. If that is the case then you donβt need to worry about it the spots will not harm your zz plants. πͺ΄ I have hard water as well and some of my plants also do this including my zz plant πͺ΄
With zz plants their older foliage can get white spots. The reason behind these βspotsβ is over time when watering your plant, the leaves can excrete some of the minerals that are absorbed through their leaves. They will show up on older leaves as white spots. This may be the case with yours. If that is the case then you donβt need to worry about it the spots will not harm your zz plants. πͺ΄ I have hard water as well and some of my plants also do this including my zz plant πͺ΄
I agree with @SuperbRaspfern . I generally use tap water because I have so many plants, but sometimes I need to wipe down leaves that get a build up. I take some rubbing alcohol and wipe leaves down and for plants that get a build up, I try to bottom water more with drops added to water.