from your description (i'm just guessing from that because it's not real clear) but it sounds like your tank to bowl rubber washers may be leaking. and it's very simple to replace them as long as you can get the bolts out (hopefully they are brass or stainless). Turn water off, empty tank, take bolts and washers out, put new ones back in (rubber washers lightly coated with a lil plumber's grease), snug 'em up, turn water back on, check for leaks. If it only leaks when you flush, then it's likely the donut gasket (some call it a spud gasket). May as well replace that while you have the tank bolts out and the tank empty anyway, just take your line loose and turn the tank upside down-you'll see where it goes.
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