Leaking tank

[Bartman]

Tank has never been empty except when it was moved, twice. Last time was about 1.5 years ago. Only empty for a day or two. Tank has been up for about 9+ years.

I have torn down and wrestled the tank outside. I cleaned and filled it with water and have found the leak while scrubbing the silicone with a toothbrush. There is a leak in the back left corner about 3-4" up from the bottom. Can I redo this spot/side or do I need to redo the whole tank?