Blossom can fade pretty easily!
The one on the bottom looks like a Year 2 Blossom who has faded. I'm not sure about the one on the top.
Here's a quick summary of Hong Kong, concave foot Blossoms:
Year One - Hasbro starts making flat-foot ponies but halfway through the year they switch to the concave-foot molds, which don't tip as easily. We know this happened because collectors have found mint on card concave hoof Collector Ponies on the Year 1 backcard.
Year Two - Blossom and Cotton Candy are rereleased with the set that includes Bubbles, Sunbeam, etc.
Subsequent years: Hasbro releases the Collector ponies as mail order ponies in various years. This happened at least three times. There may be color variations between the mail order ponies too, since they were sold in different years.
The only thing for certain is that the flat-foot versions of the Collector ponies were only sold in Year One, in stores. And everything is up in the air for the concave-hoof versions.