Guild Wars 2

Sudden Maximum Health Decrease, Warrior, level 80 with over 317 unspent skill points

Before my maximum life (that red dot in the middle of the screen thing) was 20300, but now it has for some reason dropped to 18972.
This happened not long after I got killed when trying to get to Grenth event. I got killed and after going back to nearest WP I noticed my life (again that red dot in the middle of the screen thing) was only 18972- this value is when it is full and no one is attacking me.
I do not understand how this could happened since I did not change anything on my character (traits,armor,equipment,skills).
MY VITALITY before was the same as it is now, it is just my total health bar(red dot) is only 18972.

A) How/why this happened and what should I do?
B) Is there any formula how I could check what my maximum health should be?

Thank you very much.

Update : Now my health went up to 19162.
As i said this is without any boosting items such as cookies and etc.

Same
level 65 engineer
health decreased from 22558 2 days ago, 22347 yesterday, 20128 today.
Don play this character. It stand in one place. Don’t move don’t change anything.

It means the server you play on recently held World Bonus’s earned through World Vs World.

I do believe Squall has your answer, the reset was last night or the night before.

Turial.1293:

I do believe Squall has your answer, the reset was last night or the night before.

Correct. You get an increase in health because of ‘Robust’. As the WvW matches reset on friday you lose that bonus in health.

Just press B and you will see the bonuses your characters get because of WvW.

Also: http://wiki.guildwars2.com/wiki/Power_of_the_Mists

Wow, that was just straight forward.
I feel really silly now.
Thank You All for help.