The problem you could be having is new homes shrink due to the wood construction drying out, new showers and tile also have a film on the edges that should be cleaned before application. All of the above advice is correct, silicone is easy to apply but you have to take your time and lay a nice even bead and skim it with your pointer but I have found that the gesture finger is the perfect width for a nice shower tub bead. When you are dealing with new construction sometimes you have to strip and reapply the silicone every couple months until the house is seasoned, in Michigan 6 seasons is the rule of thumb I suppose it would be less in California.