There are multiple possible causes for droopy leaves such as changes in location or watering issues.
Leaf curl can have a bunch of different causes including too much light, overwatering, cold and overfertilization.
Don’t panic. Some degree of leaf loss is normal in all plants. Whether you need to take action depends on the amount of leaf loss.
The white grains are mineral deposits excreted by the leaves. You can easily remove them by gently wiping the leaf, or just leave things as is.
Bugs are a common problem with houseplants in general and unfortunately, Pilea peperomioides is not exempt from this.