Street Scene From 1978-82

Hello everyone. On December 7, 1977, Canada Post announced the release of three Canadian street stamps consisting of 50¢ Priaries, 60¢ Maritime and 75¢ Row Houses. The 1977 release was canceled and re-released in 1978. The 60¢ stamp was issued only in 1982 with a new design that now showed Ontario Street Scene instead of Maritime Street which was awarded the 80¢ stamp. Is there more information somewhere to explain this change of image? Can't find it....

I believe it was all due to just a standard rate change which happens over time and requiring new stamps. They just used the images they wanted to and sticking with the same street scene theme.