The fish should be OK, and the filter bacteria too, but keep an eye on your levels just in case.
Overdosing the last bucket was the right thing to do. But for future reference - add enough dechlorinator to treat the whole tank, not just the new water, as soon as you realise you've forgotten. You could always go and add a bit extra now, just in case.
There is a reason for this. Fish, and plants to some extent, secrete organic chemicals. You'll read of things called DOCs in tank water - that's dissolved organic chemicals, those things secreted by the fish. DOCs react with dechlorinator so it then can't remove the chlorine. So if you add untreated water you need to add more dechlorinator so there's enough to remove the chlorine.
People with really big tanks use hose pipes to refill after a water change, and they obviously can't dechlorinate the water before it goes in. They use enough dechlorinator to treat the whole tank, adding half before they start and half after they've finished.