Hi! I can't access your
plant picture because I'm not a member of that particular site but I looked up info on Peperomia in one of my reference books; perhaps the following will help.
(I'm paraphrasing the info)
Place in full light in winter, bright indirect light while actively
growing. Water sparingly in winter with tepid water and moderately in summer. From
spring to Summer, maintain moderate to high humidity and mist twice daily applying a balanced liquid fertilizer monthly.
There are a thousand or more species in this genus so the care instructions a somewhat general but if you follow them an pamper the
plant a bit perhaps it will fill out on its own. Again, hope this helps!