a) Temerature range. 76 degrees
b) pH. 6.2
c) GH. don't know, but water is very soft
d) KH <1dH out of tap (although I've added crushed coral to raise the pH slowly over a couple months from 5.4 to the curent 6.2 so the KH is probably higher now.
e)Ammonia, Nitrate, Nitrite, levels. 0, 0, & 0
f) Water change frequency 30% every 2-3 weeks.
2. Tank set up
a) Size. 33 gal long tank
b) Substrate. 50/50 flourite/gravel mix
c) Filtration. 1 Whisper 20/40, 1 AC150
d) Furnishings. Moderate to heavy live plants, 2 bog logs, 2 plastic caves.
e) Other tank mates. 3 Glass bloodfin tetras (2 others died in past 2 months, they are all over 3 years old), 4 ember tetras, 3 paleatus cories, 4 adult, 1 juvenile panda cories, 4 habrosus cories, 3 otocinclus.
f) How long has it been set-up?
3. Symptoms / Problem description
Past few weeks one of the habrosus has been tipping over onto his back when he stops swimming. He's able to swim level, but tips over otherwise. He is not flashing. His barbels are missing, but no obvious degenerative process going on near his mouth. He is learning to keep himself upright by wedging a tail between bits of gravel or resting between a tankmate and the glass. His dorsal fin is clamped. He's breathing normally. A second habrosus has recently flashed a couple times, and both his dorsal and caudal fin are clamped, he's also breathing normally. His (and all the other cories except the one above) barbels are fine.
4. Action taken (if any) Observation only.
5. Medications used (if any) Not sure what I'm dealing with. Would prefer not to medicate the rest of the tank if not necessary, but these little buggers are going to be hard to catch and put in a quarantine tank in my planted tank.

Any advice would be helpful. Thanks.
Amy