I haven't got fritzing and due to my limited internet connection at the weekends it will have to be tomorrow before I can look at it.
However in the mean time you can do some tests.
First off do you get the default rows with no other input?
Next change the numbers that initialises the ledBuffer, are these change reflected in what you see on the LEDs?
Now change the wiring so that only one cathode is connected into the TLC5940, that is only have one LED per column on one of the rows. Can you change those numbers in that one row and see the effect?
I looks like you have not wired up something correctly, what type of FET have you used, it should be logic level P-type, and check that you have identified the drain and source correctly.
It could be that all the rows are being powered at the same time if the above is not right.