Clear and white tips indicate regrowth unless the white/clear parts are fuzzy or weak-looking. High nitrate or ammonia really doesn't have anything to do with the color of the rot - when necrosis sets in, usually tissue will turn brown or black.

Fin rot can either be a fungal infection (this would be the type that would produce a whiteness on your Betta's fins, and would rot the tail in a more even pattern), or because a bacterial infection (the tail will rot in a more ragged manner). Sometimes the viral and bacterial infection can be seen together. With the proper treatment, fin rot is usually NOT fatal. However, it is extremely important that you treat your Betta's fin rot early. When fin rot works its way up the tail of the fish, it can infect the main fish body, and cause death

MELAFIX IS VERY BAD FOR BETTA FISH!!!! The medicine you are currently using (Melafix) is a herbal medicine that is essentially neosporin for fish, it only helps heal cut fins and promote regrowth. Melafix if not used properly will burn their gills or lungs and suffocate them (by coating their labyrinth organ which is the Betta fish's most important organ... its lungs!!) The medicine should be applied to its fins and body ONLY making sure to keep away from their head by using a paint brush. You also should not put them right back in their tank after using it so that you dont run the risk of suffocating them. (Which personally that just sounds like it would be too hard to do, how could the fish survive out of water...) The concentration of the chemical used to heal torn fins in Malafix is too high for Betta fish or any other labyrinth fish to handle. People instead will often tell you that you should be using Bettafix/Bettamax which is basically the same thing as Malafix only it supposedly won't harm your beta because it has less of a concentration of that certain chemical... though if you look at the suggested dosage it would end up being about the same as using the Marafix when the two are compared. Though some people have claimed to use these products without any problems they cause lots of stress to the fish because they are so toxic. If you still choose to use these types of medicines they would only be beneficial to use after you have killed the infection because it really only promotes regrowth and healing of torn fins. In all actuality clean water and aquarium salt are the best things for healing hurt fins.

Be careful... continually giving your fish medicine will over medicate your fish causing him to stress out and letting its immune system weaken where it will catch fin rot frequently. Go to your pet store and get some Jungle Fungus Eliminator this should cure the bacteria infection. If that does not work for you I have also heard that tetracycline powder works well also (it does cause a slight discoloration of the water). Be careful when reading the instructions most of the dosages are for larger tanks- if you google it I'm sure there are some tricks on how to figure out the correct dosage for smaller tanks. The medicine may cause your fish to be inactive because the medicine is hard on them.

Since this is a common thing make sure you are not overfeeding your fish (extra food causes growth of bacteria that commonly causes fin rot), also check the date on your fish food because food that has gone bad can also cause fin rot. Doing water changes daily for one week after treating him for the fin rot will really prevent it from coming back. Don't get discouraged it can take up to 4 weeks to cure the infection. Keep adding the aquarium salt every time you do a water change because that really reduces the fishes stress levels. Once it is cured if you notice it coming back at all even slightly... immediately change your betta's water (and then continue once a day for a couple of days), because if caught early fin rot can be cured just by water changes.

And if you want to go really crazy they do have vitamins for betta fish that will boost their immune system!