Well You have obviously contacted Necro in relation to this as well and I Second his opinion however I am leaning towards Poor water conditions as the base reason for this type of situation...
Judging from the skin Color, the eating habits and the puking I am 99% sure that you have water quality issues, with the other 1% being that you have introduced a parasite (Which is possible with the live foods but unlikly as you mentioned that your RTC has always been a light eatter)
If there is one thing which is virtually ALWAYS an issue with people that have Large Cats it's their Filtration systems... They always try to match the filter to the tank instead of to the inhabitants, They have it right in Japan where they filter the fish waste and not the tank size which is why they can have a 10' gigas in a 11' tank and it shows healthy color.
Having a fish like an RTC is harder you might think, as their volume of waste grows so fast that filters can have a hard time keeping up, which can cause the filter to crash altogether and start your cycling process all over again. Add into the mix of all of that a puking RTC and your Filtration will fail almost certainly!