bottom fall out{v. phr.} {informal}
1. To fall below an earlier lowest price.
The bottom dropped out of the price of peaches. 2. To lose all cheerful qualities; become very unhappy, cheerless, or unpleasant.
The bottom dropped out of the day for John when he saw his report card. The bottom fell out for us when the same ended with our team on the two yard line and six points behind. [TahlilGaran] English Idioms Dictionary ▲