Discolouration of the electrodes is normal and typically only a cosmetic issue. It will not adversely affect your iontophoresis treatments and is merely calcification caused by the tap water. The electrodes are consumable items, so in time will require replacing, however you should be able to ‘lift off’ most of the scale with a periodic 30 minute soak in vinegar.
If you start getting connection problems (no dive light) or intermittent / fluctuating current or service, you may want to consider replacing them. Stainless Steel electrodes tend to weather better and are more resilient to scale but do not use these if you have an allergy to nickel or chromium.
If there is an issue with your iontophoresis machine, we will always be happy to look at your equipment for you free of charge (you would need to pay to ship it), regardless of when you purchased it, so it does not matter that it was two years ago.