Both level 15s on one of the accounts I use to store stuff on got 19 of them today.
All my level 50s only got one, so can you send me the missing ones by mail or something ? 
Edit : actually, ALL the characters on that account, including the level 50 on it, got 19 and now have a stack of 20. All the characters on my main account got only one 
Got 19 on my main might it depend where you had them stored? Mine were in the bank at the time
After logging in a few of my characters on different accounts, this is the pattern I’m seeing:
If you used the second day’s Tachyons you only get one today. If you still have them, you get 19.
Thank you for the report. We’re aware of the issue and looking into it now - will keep you updated!
Sounds plausible. I never ran a single DA on the other account.
We will be fixing this issue in tomorrow’s patch. Please note that if you have more than 2 Stabilizing Tachyons in your inventory before the downtime, you will be set to own exactly 2 Tachyons after the servers go back up.