Did the dishwashing solution contain any ammonia? I find most do not contain ammonia are a safe method of cleaning jewelry, including pearls. If ammonia was there, that "could" account for some of the discoloration. Also, chemicals and salts in the air in the beach environment are known to cause problems with jewelry. Even in almost invisible amounts, these chemicals can work to cause smudges and discoloration on gold items. Generally, a regular cleaning like you did will prevent problems.

Is the bracelet gold? The color change is not a direct indication the item is not gold as marked. However, there should be a makers mark near the 14k mark. That is law at least in the U.S.A. and the mark should be there. Sometimes the mark is quite small or only a symbol of some sort, perhaps mixed with the 14k metal quality mark.

Do you have faith in the place the item was purchased? If reputable, there should be no problem and they might offer to clean and buff the bracelet or even replace it.

If purchased with no recourse, the only way to truly tell is to have a jeweler who will test gold run a test for karat on the bracelet. These test involve either a simple acid test or use an electronic instrument. The cost should be low. Call and check around before you go since some jewelers do not have anyone on the premises who does this testing. Almost any store with a working bench jeweler should be able to test the bracelet.

If this is gold, why the color change? One possibility and only a possibility is that the bracelet was given a quick flash plate of yellower high karat gold to make it look richer in the first place. We see lots of necklaces and some bracelets(lots with CZ stones) with a plate of very yellow high karat gold. This is all for merchandising to make the color more rich and perhaps more appealing. Unfortunately, repairs will easily remove that surface plate and leave the natural 14k color. The 14k color is just fine as it is! However, some of such plated items do show a more coppery look when the surface flash of gold is removed, perhaps an underlayer used in the plating process or the natural color of a less than attractive 14k gold mix which the maker knew would be flash plated to look rich yellow. I doubt the cleaning or polishing cloth removed the plate.

I simply suspect the environmental conditions led to the discoloration but that should be rather easily removed by a good wipe with a special jewelry polishing cloth. (Your cleanng would remove ocean air salts but not repolish the bracelet or remove tarnish unless a jewelry polishing cloth was used.) These special coths contain no messy polishes but do contain some chemical ingredients. One make is called "sunshine" cloth, used as is till totally soiled then simply disposed of. These cloths are available from jewelers and crafts stores. If not in stock, this cloth may be ordered for you.

My first suggestion is to have a jeweler who does metal tests check the bracelet if the item was not purchased locally and cannot be locally corrected. Then, if 14k as marked, get one of the cloths mentioned(or a similar one). Clean regularly just like you did being sure there is no ammonia in the cleaning solution.