I looked up S. margaritae, Japanese Spirea (Spiraea x bumalda 'Neon Flash'), and several other plants, but S. japonica 'Neon Flash' seems to be the best fit. The description and pictures match. I am going to continue my research, but as of now I think these are S. japonica 'Neon Flash'. Thank you everyone for pointing me in the right direction and all of the much needed help.
@greene @flaflwrgrl @plantladylin
