I've planted two zuchini plants, the type with round fruit, the plants are doing fine and have fruit. But the fruit aren't getting bigger and the oldest seems to be rotten. The same thing happened last year with regular long type. The fruit comes on but doesn't reach full size before it rots on the vine. Any ideas? Thanks

Sounds like "blossom end rot" check this link Squash Blossom End Rot Causes And Treatment (http://foxyurl.com/3uv), also Solutions For Common Problems Growing Zucchini (http://foxyurl.com/3uw) .