Problem with multiple tlc5940

I think you are running out of memory.
The library says:-

/** The default fade buffer length (24). Uses 24*13 = 312 bytes of ram. */

When you add a fade you are not checking if there is room for the buffer. It says in the library

/** Adds a fade to the buffer.
\param fade the fade to be copied into the buffer
\returns 0 if the fade buffer is full, fadeBufferSize if added successfully
*/
uint8_t tlc_addFade(struct Tlc_Fade *fade)

so in place of doing simply the tlc_addFade
every time you should do:-

if( tlc_addFade( ........ ) == 0 ) Serial.print("error no room");

You need a Serial.begin(9600) in the setup function.
Then run the code and see if you get any error print outs.