Welcome to the group.
You have a couple of problems here. First, your tank is way overcrowded. By the time you add live rock, and a sandbed that 29 gal tank is down to about 22 gal of actual water. In a SW system you usually want to maintain a stocking limit of 1 inch of fish for 5 gal of water. In other words, you want a total of about 4 to 5 inches of fish in your tank. Most of the fish you mention are likely about 2 inches long. and you have 5 fish. This puts you at about double of what you should have in the tank.
As you have noted, you only have about 16 lbs of live rock. In a reef system the live rock is the biological filtration system, so by having less rock, you have less biological filtration. This puts more stress on the livestock.
You also have a new system, and it is possible that it was not cycled or that it was stocked too quickly. There isn't too much you can do about it now, but the suggestions to test your water are good ones.
As for the spots, there is a FW fish disease called ich and it's the parasite
Ichthyophthirius multifiliis. In SW there is a disease that look similar, but it's a different parasite
Cryptocaryon irritans, so it gets the same name. Treatment for the SW disease is completely different. Here are a lot of links on the site to it's treatment.
http://www.reefsanctuary.com/forum/index.php?threads/marine-ich-myths-and-facts.23132/
http://www.reefsanctuary.com/forum/index.php?threads/copper-treatment-use-problems.23130/
http://www.reefsanctuary.com/forum/index.php?threads/curing-fish-of-marine-ich.52236/
http://www.reefsanctuary.com/forum/index.php?threads/a-hyposalinity-treatment-process.23131/
It's a lot of reading, and it's quite an ordeal to treat the disease. To summarize all this -
Make sure they really have the disease.
If one fish has it, they all do. You must treat all the fish.
The only really effective treatments are copper or hypo salinity.
Most if not all other treatments don't work, despite what other might say.
Treatment must be given in a quarantine tank and should run for at least 2 week after you don't see any more spots.
The display tank should remain empty of fish for 10 to 12 weeks, so any parasites in the tank can die off from lack of a host.
Good luck with treating your fish.