tlc5940 and led strips

Hello

so i got the strip and i cut an 10 cm strip of it and did some testing. but the readings somehow confuse my understanding of how this should work :frowning:

if i measure my power source directly without anything hooked up, i get 12.30 volt. which is ok since its a 12 volt power source
if i connect the common anode and the blue cathode directly to the power source (without resistors or anything) i get 12.16 volts on the blue line. which seems high. shouldn't leds have a higher voltage drop than 14 mV ?

i then used a transistor setup. common anode to the power source, 3 transistors (one for each cathode ), no resistors and cycled the colors with the arduino and i only measured the blue line again.
then i get:
if blue is off, 4.20 volts
if blue is on without any other colors 12.12 volt
all colors on 11.9 volts

this confuses me

has anybody any advice on why this is or if i am doing something wrong ?

thanks

EDIT: i always measure between anode and cathode (holding the measuring wires directly on the anode and cathode wires)