could be an issue if there is not enough adequate hiding spots and if the newbies are not close to the same size. other than that, should be no problem, just a matter of time till they start shoaling together. That and hopefully you have a big enough tank.
My 5 inch reds got tail nipped for about a week when I tossed in my 8 inch yellow tern, but then they started to get along and he shows them the ropes, so to speak.
50 gal for 5 Ps will surely result in injuries or even elimination. 3 is enough to establish territorial space, but 5 would be too crowded. Unless these are still babies (3") and your planning to upgrade within 2-3 months to a bigger tank, then I say wait to get a bigger tank.
i added 3 2-3" reds with my bigger ones
my secret was i added vines to half of my tank and lots of feeders
my big ones were inrtersted in the feeders while my babies spent most of the time in the vines
now the vines are out and they shoal nicely