I have planted 5 new citrus trees in the timeframe ranging from Oct '09 to Feb '10 (lemons, oranges, mandarin). All of them bloomed and set tiny fruits in the spring/early summer. There has been excellent vegetative growth and progress on these trees this summer.
In the last few weeks, at the tip of all the newly emerging branches, all of these trees are putting out a second round of blooms. I am wondering if this will affect the fruit quality of the already set fruit? And is this normal behavior? My mature (15 yr old) navel orange tree does not behave this way. All the young new trees are now sporting a bunch of blooms Thanks for your help.

This is normal behavior. Most citrus have 3-4 flushes of growth each year, with flowers in the first spring flush. However, sometimes flowering occurs in the other 2-3 flushes (it occurs often in lemons, limes, and kumquats). I have never seen it in a mandarin but have seen it in a grapefruit. I wouldn't be concerned...in a mature citrus tree, it will set fruit and keep what it can handle and drop what it cannot. I probably wouldn't be letting the young trees fruit anyways.