coolant leak help!
 

i have a 04 s4 and i noticed a small puddle of coolant on the ground anytime i drive anywhere and park , its dripping slow from the passenger side bottom corner of radiator, my shop said they did a pressure test and nothing, they said they dont see a leak, is my radiator busted? also mayb 1 nce a week my temp gauge would drop to low for a couple seconds and go back to normal, no other symptoms, i dont see any cracks, car doesnt overheat,

thanks for ur opinions