remove the dead sealant (but also check the rubber boot above isn't the real reason for the leak).
tightening the bolts won't do anything.
upol tigerseal is the best stuff. (haven't I said this to you already?), put it on the panel then tighten the bracket back on so it squishes round the bolt.
if it is leaking it should be a teeny tiny amount, if it's a big leak then this isn't your cause.