Make the polkas bushy/short

So I have a small sized one with Fittonia, Polka dots , English dwarf ivy and moss. It is near a large window receiving enough indirect light. The polkas are growing aggressively vertically and this is second time they've started pushing the cork. If I trim, instead of growing more branches, they just grow one long stem with long gaps between leaves. What do I need to adjust? Light (enough), water (keeping an eye, open the seal once every month)? Thanks!