Posted: 06/08/2013 at 20:02
Plum Royale is one of the ones which in theory should be OK in sun (see http://www.plantagogo.com/acatalog/HEUCHERA.html ) I've had great success with heucheras in full sun - see this sheltered south-facing border in our old house, 1st pic in 2003 and 2nd/3rd in 2005) - these all started from 1-2 litre pots.
I'd keep taking the brown crispy leaves off and do as Verdun suggests re checking for vine weevil/reinvigorating if no sign of vine weevil.
Fingers crossed, but if your current one doesn't thrive I'd recommend contacting Plantagogo (see my link higher up in this post, they have a facebook page as well as a website) and asking which ones are likely to thrive on your balcony. Good luck!