Adding Recessed Lighting to bathroom circuit
If a circuit has bathroom receptacles on it, you have two choices and the circuit must fit one of them:


The circuit powers only receptacles, in any number of bathrooms. Nowhere else.  
The circuit powers receptacles in ONE bathroom, and any ther hardwired loads in that same bathroom only.  


Now if the circuit predates those rules, you are grandfathered insofar as you don't change anything, but if you do, you can't make the situation worse.  So for instance if a circuit powers 1 bathroom receptacle and 2 bedroom receptacles, you can't add a hall light. 

So if the downlights are going in the bathroom, that is fine.  However, you don't want a situation where someone trips the breaker running both a hairdryer and a curling iron simultaneously, trips the breaker and plunges themselves into darkness.  Then they're in the pitch black holding a hair dryer, which they accidentally set down in the sink full of water. Then when they reset the breaker, the GFCI trips and the hair dryer is ruined.  At best.