Franja

slabéti to weaken, to grow weak (ali feeble); to diminish

poslábšati to make worse; to aggravate; to deteriorate; to impair

poslábšati stvari to make matters worse
in kar stvari še poslabša... and what makes matters worse
poslábšati se to change for the worse, to worsen, to get worse; (položaj) to deteriorate; to grow (ali to get, to become) worse; to become impaired; (zdravje) to deteriorate; (slabeti) to go from bad to worse, to sink, to flag