dnd 5e – Do my players know the specifics of an enemy’s attack

As you’ve noticed, there isn’t anything specific that details a mechanic on players ‘learning’ what to do.

This becomes a DM decision and you’ve got lots of ways to approach this. Depending on the condition/action I’ve done everything from a skill check to know to simply telling them. It very much depends on the situation, the players, and the table, but picking what ends up being fun is really your core decision making process.

As Thomas Markov says in his answer, the cost of using an action for most of these is still pretty big in the action economy. Forcing more time to figure out what to do could be unfun, but talk to your table and see how they and you would like to handle this.

Player creativity

I’d also be very much open to allowing different actions to resolve the issue. The players know what’s wrong and they can be clever – and we should let them be clever. If they come up with an action that does the job, let it do the job! It doesn’t have to be the specific thing, but saying, you can try to put it out may be enough to lead them to water.