Hey 0kgvtof28zrz,
Sorry to hear that some of your crystals have disappeared unprompted.
If you haven't already, please contact in-game support for missing content with your Player ID handy. You can do so by following the steps below:
Settings > Help > Select Contact Us on any SWGOH help article and follow the prompts (more information here)
The team there will have the right records and tools to look into this with you, as we're unable to support account-related requests here on the forums. It might be worth checking whether there have been any foreign logins and securing your account, in case it was accessed by someone else.
Let us know how it goes, thanks!