Proper and consistent emulsion control is of the utmost importance in achieving good results on a complicated print. Make sure that the screen emulsion is correct, meaning there must be enough emulsion on the bottom of the screen (the side that touches the shirt) to control and contain the ink being deposited.
Think of the emulsion as a gasket; if you have a leak, then the ink will spread. This will cause the ink dots to begin to touch, commonly known as dot gain. Sometimes this can be difficult to control due to variables like the type of shirt fabric, but the better the ink containment, the better the results. This all boils down to the emulsion coverage on the screen.