I do not keep track of player HP, spells slots, conditions, etc. This is your job
I am OK if players share their HP, spells slots, etc. with each other. If you find it fun - share it. If you find it fun not to - the do not
As for enemies
I. When you are facing an enemy you have never seen before you have no idea how much HP it has or how close it is get KO or killed.
II. I will share exact HP if you fight same type of monster again in this game
III. I allow PCs to spend action to roll history check for anything they touch, including enemies. A passed history check means that you happened to have historical experience of such thing (i.e. in case of monster you may recall amount of HP or even resistances/immunities). DCs are usually between 10 and 15 but depend on PC and monster. For Mal as Bugbear DC to remember anything about special type of goblin could as well be 5 while 15 for Lizard Cleric.
P.S. Experience with PC HP sharing -
Some players post OOC their HP and status with each turn post.
I find it strange but I am not against it.