I don't know if beautiful here applies to a man or a woman. If it's a man, you say "...,mein Schöner!", if it's meant for a woman or a girl, you say "meine Schöne!".

But this literal translation of "beautiful" isn't used very often in German(y). If you want to write this sentence to a friend, you can use the expression "Süße"(woman) or "Süßer"(man), which means sth. like "sweetie". If you are in love with this person or it's your child, you can say "Liebling" or "Schatz", which means "darling" or "honey" or....

"Gute Besserung!" is also used as the formal expression of this wish, so you can use it for you colleagues, too.