(figuratively) to be exhausted, to be asleep on one's feet, to drop from exhaustion

to be knocked down a peg, to fall from one's pedestal

to fall into ruin, to go to ruin, to fall into disrepair, to be tumbling down

(simile, informal, derogatory) to drop like a bad habit, to drop like a hot potato

at breakneck speed, hell-for-leather

to fall from grace, to fall out of favour

(simile) to come as a hammer blow

to snow in large flakes, like the white furred skin of hares

to fall out of favour, to fall into disrepute

(simile) to drop like flies