The problem is there are 2 places where silicone is used, between the panes which is what actually gives the bulk of the tank's strength, and then there's inside the corners which tends to help a bit with leaks, but really is not necessary for stability of the tank.
If you were to take off the front pane, and clean all the edges of the tank there's going to be contact points where the silicone from the front pane touches the silcone from the side panes where they connect on the bottom pane. You can't get a bond where the old silicone touches the new, so there's always a chance of a hair line gap between the new and old silicone..
Now is it possible to salvage this? Sure. The sure fire way is to remove all the panes, and resilicone the whole thing, this is a level of skill of doing this is somewhat high though. An alternative would be to just resilicone the front pane, and scrape off all the interior corners silicone and then redo all of that, yes you may have that hairline amount that doesn't have a bond between the front pane and the side panes where they meet up at the bottom pane, but the inside corner silicone job should keep water from getting to the actual strength joint. But you have to remove ALL the inside corner silicone, because again you will not get any bonding where old touches new. Just remember that the more time you put in prepping the job, the easier, nicer, and more effective the job will be.