Ektar is a high contrast film, so your process must be dead on and your light sources the same colour. Shoot some colour patches to check your process, and then try some different conditions. The price you pay(as in b&w) for fine grain and high sharpness is that with a contrasty film, changes happen very quickly. This is not crossover, this is actually a sometimes uncomfortable level of accuracy. Our brains make a lot of adjustments without telling us- we 'know' that the shadowed part of an object is the same colour in a Platonic sense, but the actual reflected light is dependant on the light falling on the object. There is a reason why low contrast films are popular with wedding photographers. You not only have lighting issues on both sides of a face, you have multiple complexions in a group shot, and you are never allowed to make the blue and green people blue or green, but you must keep the ruddy from looking hypertensive(or crazy).
So, Portra will make you look good, but you must make Ektar look good. That being said, you want a finicky film when setting up or checking your processes.