aah bro… there is no straight answer to your question about what to do with this stocks… no one knows what will happen next, maybe the stocks will bounce back, maybe they might keep falling more… as i said there is no straight answer… best that you can do is do research on fundamentals of stocks you have invested in and get rid of bad ones.
I guess there is no straight forward answer to the question. It mainly depends on the company you are talking about. If you believe in the company it is always advisable to just keep the stock in the portfolio. However if you feel that there are less chances of revival of the company you could always sell them and exit. However if you go by my suggestion, always use stop loss while trading, thus if prices go against you, you could always exist beforehand and re enter position only when you feel like again.
P&L realised from closing a trade is called as Realised P&L, this amount gets added to / debited from you account balance. P&L you see for stocks you are holding is known as Unrealised P&L, unrealised because you haven’t closed the trade yet and this keeps fluctuating according to your buy price and current market price this unrealised P&L doesn’t get added to / debited from your account balance.
Average it or keep adding to make it up for the loss if you still think it has got something left in it. Otherwise as Italians say “forget about it”.