I use a 3 group La Cimbali at our coffe shop and our espresso shots seem to be a little bitter. I have gone from checking the beans, making sure they are in an air tight container to our grind (about the equilivant of very fine sand), to the temperature of water (about 190). Also when I pull a shot of espresso I can look in the small metal pitcher and just almost see the espresso through the crema. Are my problems related? Any sugestions?