n1cd should have more consistent hydro, doing n2cj there's a risk of pyro overtaking usually at the 4th ca, doing n2cd usually at the 5th na, the reason why hydro doesn't stay on the enemy is because of hu tao's blood blossom ticking, that triggers pyro onto the enemy and yelan only applies 1 u per wave of strings, which is enough to cancel the pyro but not apply hydro, so you can either do n1cd, or attempt to overtake pyro with n3cd by applying another wave of hydro strings, or make the pyro infused na not land but have yelan's string hit the enemy. you can also do n3cd as you anticipate for a blood blossom tick