no probs, i wasn't 100% sure if it was you or not!
Angel's really aren't recommended for tanks under 6 months old, they need the maturity of an older tank, sometimes they'll survive, sometimes they die straight away, sometimes they'll be fine for a while then die for no reason
if the platy's died within a couple of days of going into the tank there's two main options
1 - the water conditions from the shop to your tank were vastly different and they never acclimitised
2 - they were already carrying a disease and brought it into your tank then died
to check up you should call the store you got them from and ask the pH and nitrate of their tanks, if you rule that out then you may have cause for concern as the platy's could have been incubating a disease but not shown it until they got in your tank, then passed it on to your angel, who incubated it for a week or two then died.
keep a very close eye on the tank for the next few days and do a couple of water changes to make sure the water quality is tip top. It's hard to advise if you should treat if there's no symptoms or signs off illness