I am new to this forum but not to the hobby. Most of what you have heard thus far you should trust- from what I have read of Dave's stuff he knows what he is talking about. I would like to hit a few things here in addition though.
First- before you do ANYTHING else, slow down. Your reactions may be too quick and uninformed right now, and a fish tank is kind of like an experiment, especially for someone new to this. We all know, we have been there too, checking water parameters 4-5 times a day, wondering about this, worrying about that... and if you "try" to many things, you can be disrupting that experiment daily, which makes setting a "base" (known set of factors) hard to establish.
Real quickly, pH down- not good. Creates desired effect short term, but does not solve the problem long term, so you will have pH swings due to buffer issues. This is the kind of chemistry that even I don't like to dabble in, so let me just say that for the newbie, pH adjustment and the explanations behind it are mind numbing. pH down also in most cases adds phosphates.
So- how do you address this?
First, test your well water for everything- GH, KH, ammonia, chlorine, phosphates, nitrates, etc... granted, being a well, many of those things should NOT be there, but test em anyway. This will tell you what your base starting point is with your water. I am going to guess it will be alkaline and a little hard.
Second- determine if you want to either keep fish that will like the kind of water you have naturally from the well (cichlids, for example)- OR, if you want to do something to change it that will WORK (DI, RO filters).
I would recommend Aquarium Pharmaceuticals "Tap Water Purifier"... basically, it is a DI unit. About $25-$30 online. Will make your water fine for Characins/Tetras, if you want such fish. I use one religiously. Follow the instructions, filter the water SLOW.
So- drop the pH down, and either adjust your ideas on what fish to keep or use a "real" solution to change the water hardness and pH to levels you desire. If you continue to use pH down and try to keep low pH fish, you are going to wind up hating the results.
Other quick points:
1. IMO- that pH (8.0 and up) is NOT good for Glowlighs, or other Tetras.
2. What are you using for substrate? This could be causing the high pH (although I doubt it)... stranger things have happened though...
3. Fish wil generally adjust to pH ranges outside of what they prefer, as Dave said. However, they REALLY do not like big changes that "shock" them. On a cellular level, this can effect them profoundly- gill functions, etc... So, you really should be careful bringing fish home from the store- find out what their pH is, and if it is more than say .5 off from yours, I would do some more extensive acclimatization. I suspect this is the cause of your fish sitting in the corner and not eating.
4. Temp is fine. Do you have anything in the tank for them to swim around, give them the impression they have some "cover" if they need it?
5. Food- you could try some frozen brine shrimp. Shave a very small amount/chunk off, and toss it in... not too much. They might smell that and like the look of it as it sinks more than the floating flakes.
Being new to this is fun and stressful at the same time. Do yourself a favor and get some good books on the "hobby". All of the Baensch Aquarium Atlas books are great. Spendy, but very extensive. They will really open up your world of knowledge on this, and you will quickly have tools to make these tough decisions seem easier.
And of course, people on here and other site like the Krib are great sources for info. Just be sure to get a broad opinion base on serious issues, and not just take the word of one or two posts because you are worried about your fish.
Good luck!
