pixieil,
I don't think you need to start a new topic, unless you WANT to. I have a male betta that went through fin rot. It was horrible, just overnight, without any warning, most of his tail fin was gone, and it was rapidly eating at his top and bottom fins, too.
What *I* did...At the time, he had been in my 10 gallon tank, with the tropicals. I took him out, put him in his own little 1 gallon tank, and added about a teaspoon of aquarium salt, and added about 3 or 4 drops of melafix per day. I also did complete water changes for him about every other day. He didn't start blossoming right back out, but it stopped the deterioration, which was my biggest concern. Once that was under control, I noticed that he also has black spot disease. I stopped the melafix, continued the salt, and started treating with tetracycline as well. I started doing almost daily complete water changes, now it's back to about every other day. The tetracycline has not only helped with the black spot disease, which is almost gone now, but it also seems to be promoting more rapid growth of his fins.
Also, you say that your fish is white, so it's hard to tell if he has ich for sure...
I also have a white male betta (the one I talked about previously is my red one) It IS more difficult to tell on the white fish, but try holding your fish (in a bowl or whatever) in front of the light. Watch for him to spread his fins out, and if there are tiny spots where light won't filter through on him, then that would probably be ich. That's been the best way for me to tell, holding the bowl up to the light, and waiting to see what it looks like when his fins are fanned out.
Best of luck, and let us know how he's doing
By the way, I'm trying out a new medication for external parasites right now. It's supposed to be a three dose thing, every other day, and they're not due for their second treatment until tomorrow. I'll let you know how it works out.