Hi,
Translucent tips on Ferns are not normal. It doesn't occur in natural systems all that often so that must mean it's something we're doing. So it's normal.....in the sense that it is normal for us to screw things up.
There are a couple ways to fix this, by simply adding lots more CO2. Of course you would immediately annihilate your fish, but then the problem of translucent tips would go away. You can also drop the temperature in the tank an turn all the lights off. The ferns will grow very slowly just with ambient light only, without translucent tips. All the other plants would fade away though, and it would be boring to look at a dark tank all the time.
If you don't like the idea of having your fauna disappear, or of removing the lights from your tank, then just live with this normal condition and carry on. It's not really that big of a deal.
Cheers,