OK, there are several things that could be causing your plant to wilt.
1. Not getting enough water. If I understand correctly you've got a recirculating bubble bucket system, where the nutrient solution circulates through the buckets and keeps the buckets topped off. So it seems to me that underwatering is unlikely.
2. Excessively high air temp. You say that you don't have a temp problem and the other plants are doing well, so I'll assume it isn't an air temp problem.
3. Insects/pathogens/disease. You say you have an aphid problem that you have under control. I'd be more worried about the root system; fungus gnat larvae, microscopic nematodes, and pathogenic fungi and bacteria can reek havoc in the root zone if conditions are right for them to thrive. High reservoir temps, algae in the res, lots of dead organic material in the res, low oxygen levels, etc. could make the roots prone to attack by opportunist pathogens such as Pythium. However, you say the water is well oxygenated, changed frequently, etc. and the roots look good. If you don't have an algae problem and the water smells clean (has no odor) then I'll say it's OK for now.
4. Shock. Shock is usually caused by a drastic change in the plant's environment: transplanting, drastic changes in light or temperature, ph fluxuations, etc. I'm assuming that you haven't changed anything drastically in the last week or so.
5. Overwatering/not able to take up O2 through roots. It won't take long for wilting to occur if the plant is unable to take up O2 through the roots; it can happen overnight. Things that can cause O2 deprivation:
a. Water not oxygenated: doesn't seem to be the case.
b. Roots being suffocated by algae/bacteria or under attack by a pathogen: again, if the roots look good and the water smells good then this may not be the issue.
c. High water temperature: the roots take up O2 best at around 66* F. As the temperature increases the roots ability to take up O2 decreases drastically. Typically, you want to keep the res temp between 66* - 75* F; above 75* and you'll start to have problems. If you let the temp get into the 80's you're almost certain to see problems with O2 take up. It's hard to say that you have a res temp problem; the fact that your other plants are doing good seems to indicate otherwise. However, since you have a recirculating system it would be easy to drop your res temps to around 70* using frozen liter soda bottles in the res.
d. Water level too high or changed. Basically, your plant develops roots that take care of two functions: to take up O2, and to take up water/nutrients. Typically, the roots above the water concentrate on O2 uptake ("O-roots"), the roots below concentrate on water/nutrient uptake ("WN-roots"). If the water level is too high (above the bottom of the net pot, say) then as the plant gets bigger there eventually won't be enough O-roots to support it. If you drop the level of the water to say 1" or more below the pot then the former WN-roots will develop into O-roots. However, if the plant is used to a water level of say 2" below the pot and you then raise the level back up to the net pot, the O2 roots will not revert to WN-roots and the plant will start to suffer from O2 deprivation and wilt quickly. Basically, what is your water level set at, and has it changed in the last week or so?
That's about all I can think of. If it were me, I would isolate the plant from the shared reservoir (in case the plant has a disease or pathogen problem). I would then drain the bucket like MeisterYo suggested and let the roots sit in air for about 15 - 30 minutes. Then I would lower the water level and temperature if necessary and flush with ph-adjusted water and hydrogen-peroxide (to thoroughly oxygenate the water), and then go back to the normal nute regime in it's own bucket until the plant recovers.
Long post, I hope it makes sense and helps
