Running a bead of silicone over it, is not an option. In addition to the new silicone not wanting to stick to the already cured silicone, the curing process may not take place at all, if new silicone is placed in contact with already cured silicone.
Left with only two choices, you dilemma is less daunting. With 3 choices, there is a 1/3 (33.3%) probability of making the right choice; with only two choices, the probability is 1/2 (or 50%.) The psychology of choice is a interesting field of study. Most can choose between A or B, but many find adding a C debilitating. Couple the psychology of choice, with the psychology of information overload (too much information,) where as the volume of information increases, the instances of good information are inversely proportional to the amount available, and you have, well...a forum.
The seams show signs of abuse, however the abuse is not widespread enough to justify the amount of labor involved in resealing the tank. I suspect the tank will tolerate one more go around of abuse, before considering resealing. It is a great deal of labor to reseal a tank, and depending on who does the work, it could very well end up worse, rather than better.
If it did require resealing, I don't think I would waste the time on it. 55s (as welll as other tanks sizes ending in 5) don't make good marine tanks, as they are too tall, and too narrow, and you can't get a decent sump under them. They don't really make good sumps because they are too narrow and too tall. I would probably trash it, before putting in the time and energy.
Incidently, the green cast in the images is due to lighting, and the iron content of the glass, not copper staining.