If the enemy mage casts a spell and I describe to everybody that it becomes pitch black all around them, they know that a Darkness spell is going on. If on the other hand I ask for a CON save and (after they failed) tell them that they can’t see anymore, they know the mage cast Blindness on them.
Similarly, if it becomes dead silent in the area, they would assume that someone dropped a Silence spell. But if I describe that they can’t hear anymore (after failing a save), they would think that they are now under the influence of a Deafness spell.
But how would they know the difference? Because at first glance I would imagine that somebody inside the effective range of a Darkness or Silence spell cannot tell if a spell messes with their head or with the environment. Or is it obvious what happens when the spell takes effect? (For example, a Darkness spell expands from the center or gradually makes everything darker, while a Blindness spell just kills your sight from one moment to the next?)
Because although losing sight/hearing due to Blindness/Deafness compared to Darkness/Silence seems identical from the character’s point of view, they have completely difference options in both cases.
A deafened spellcaster can cast spells with verbal components, but a spellcaster affected by Silence cannot. They could try to run out of the effective range of the Darkness/Silence spell, but they cannot run away from Blindness/Deafness. A spellcaster could cast Continual Flame at 3rd level to negate the Darkness spell, but this wouldn’t help if he/she is blinded.
At the same time they would have to make saving throws every turn and maybe they notice that (somehow)? Then again, they are in the heat of battle and could be too distracted to pay attention to the minute differences between the various options of not being able to see/hear.
Is this something I can use as a GM to mess with my players every now and then? Or would the players feel hassled, because the differences are obvious?