Yes, those ingredients should be listed. There are some loopholes in labeling laws but I don't think they affect honey. Just make sure there is no small print that says "Honey Flavored Product" as that is definitely not pure honey. Store bought honey is often pasteurized and ultra filtered, causing it to lose much of its character. Most true honey labels I've seen at the store will state "pure honey" and will often say something like "Honey sourced from Brazil, the US, and China." In addition to being processed, those honeys may be a couple of years old before they are blended and bottled, again losing character. I started off with clover honey from Sam's Club and made some decent meads with it (metheglins mostly) but I now use local wildflower honey or I order the various varietals online. This had made a big difference in my meads. Orange Blossom honey makes wonderful mead.
It can be hard to pinpoint exactly why your mead quality is fluctuating or diminishing. Having detailed brewlogs might shed some light on the subject (If you have them, post some of them to help us determine a cause for your problems) but many things contribute: water, honey quality, yeast variety, temperature, pH, and added nutrients to name a few.
I have been home brewing since 1995 and making meads off and on since 1997. I've really gotten serious about meads in the last few years and until I found this forum I really didn't have a good resource to learn by. A lot of techniques have changed, new methods and ideas have come along in the last decade, and my meads are improving because of them. I started like many and just threw a mead together, pitched the yeast, and waited for it to finish fermenting - often 2-3 months. Adding nutrients at certain times (staggered nutrient additions) makes for happier healthier yeast, speeds things up, and even helps improve taste and quality.
Right now one of the popular methods of making mead is Brays One Month Mead (BOMM) - do a search here on the forum to learn more about BOMMs. Another good mead to start with is Joe's Ancient Orange Mead:
http://www.gotmead.com/forum/showth...lproof-Ancient-Orange-Clove-and-Cinnamon-Mead
Basically, follow the good advice found through out this forum and keep trying. One of the best pieces of advice I've heard recently was on GotMead Live in the Ask Oskaar segment. He said if you are going to make one mead, why not make four or five? Take your 4-5 gallon batch and divide it into smaller batches and experiment with different yeasts, nutrient feeding protocols, etc. and see what turns out the best.
I consider water to be one of the most important ingredients in beer and mead. City water, especially if not boiled first, may have residual fluorine and chlorine and other chemicals that can affect flavor. Some people use distilled or reverse osmosis water. I used to live in a place that had a well tapped into the local aquifer and the beers and meads were great. I now buy spring water from the store. Not much character to it but better than tap water. I have had good beers and meads made with distilled or RO water but brews made with that water can sometimes have a "sterile lab specimen" character to them in my opinion. Many of the world's beers get part of their distinctive character from the local water where they are brewed.