You need to have three instances of TTS-1; one for each track. Currently. even if each track is assigned separate midi channels, each track and channel is controlling the same instrument patch.
When you load three instances of TTS-1, each instance controls it own set of instrument patches so even though each instance of TTS-1 may be calling up the same instrument patch, each TTS-1 is controlling its own patch.
Hard to believe but TTS-1 has been included with Cakewalk DAW products since 2005. Craig Anderton wrote a very good TTS-1 tutorial for the British version of Sound On Sound. The tutorial is available at this link:
http://www.soundonsound.c...ng-sonar-4s-tts1-synth