Some of the brokers have started to request investors to reduce their margins which are prevailing for more than 10 days. The same brokers has been allowing unlimited credit despite the recent SEC announcements, due to their adequate liquidity positions. However the current request put investors in jepordy as some of the investors have collected stocks by using the margins with the intention of selling when the market is back on track, hopefully at the beginning of next month.
Unless one has liquid cash to cover up the margins, it's by no means a good idea to collect stocks, despite broker advises.
I have a feeling that now brokering firms have taken a leaf out of SEC, to surprise investors with many new criterion.