The blonde in the middle is Daphne she is Bloom(the girl with red hair) Older Sister she will be joining the winx in Season 6 and they will be showing her sirnex form. When she has her mask she is in Nypth form.
Daphne looks like oritel bloom like Marion. Siblings don't always look alike. However if you want similarities compare the eye size and shape big butterfly ones. Next look at the casual hairdos Daphne's is identical to Bloom's season 5 do just instead of pinning the curl to the right it's worn over her shoulder. Also their outfits have a lot of blue in them. Bloom is apparently their favorite color/leader colors.
have you tried the different tabs on the videos? Usually one will work better than the rest. If they still don't work I don't think I can help. That is the best website I know to watch stuff and everything works for me. Do you think its your web browser, or have you updated flash?