I think my betta has gill disease!?!?!??

Question
Hi, and first off thank you for taking time out of your day to read my question and try to help me and my betta (Ethan) out...We both appreciate it. OK, so I have a 5 gallon tank and in it I have 1 male betta, 3 tetras, and an Octo... (he's the algae eater).  My Betta for the last couple of days has been behaving weird. He hides under this cave-like bridge he usually loves to sleep in. Only now he's been spending all night AND all day in there coming out barely 20 min a day. He was always a very active fish and it's sad to see him so miserable. One of his gills, his left one.. is swollen and appears to have these horizontal lines across it, it's discolored and does not look healthy at all. The other gill appears normal. His breathing is however very rapid on both gills. He seems to open his mouth every now and then as if gasping. He doesn't go to the surface much any more... just stays on the bottom under his cave or hiding under a plant when he does come out. The water is kept warm, because i've heard that they prefer warmer water when they are sick. The temp. is about 82 degrees. I've been treating the tank with Jungle's Life Guard medicine for 3 days, since i noticed the symptoms. He doesn't seem to be responding to the medication. The gill still is inflamed, and if anything maybe a tinnnnnny bit less than yesterday but if theres a difference at all it's hard to tell. There is also Coppersafe in the tank. I always have it in there as a preventative.  He seems really miserable and i want him to get better. I've had him for almost 2 years. And, though I know that's about the length of their life span, I've grown attached and I'm not ready to let him go yet. Please if you can suggest a different medication, or anything I can do to make him more comfortable, happy and able to breathe easier i'd greatly appreciate it and i'm sure my betta Ethan would too. His ammonia level is...barely .5, though I know idealy it should be 0. His Nitrite is 0. And, his Ph is....6.4, I know that's low, so i added a ph buffer which puts it at a neutral 7.0.
He also has an air stone in his tank to increase oxygen, this has always been in his tank, and also this carbon filter is currently not in the tank because of the medication I'm using.(it said on the package to remove the carbon filter, add a half a tablet a day consecutive for 5 days at 24 hr intervals and then on the 6 th day to  do a 25 % water change and add a baterial enzyme product and a dechlorinator all for the entire tank volume. My other fish seem to be in perfect health. I don't know if i've given you all the information you need, or if i've given you too much but, I didn't know what you'd need to know exactly... so here it is.. I hope you can help soon. Thank you!

Answer
Hi Erica:  Betta fish respond better to antibiotics then they do to most other medications.  I would treat him with Tetracycline and see if that does the job.  I would also not add anymore chemicals to the water like the pH buffer... it may cause his gills further distress.  Keep me posted and when his antibiotic is done then do the following:  replace the carbon filter and do a 25 % water change and add a bacterial enzyme product (CYCLE OR NITROMAX) and a dechlorinator all for the entire tank volume.  dave