Many people face this issue of Blank, white or Empty pages problem after an upgrade in WordPress account. Many faces problem in wp-login page too. the issue is generally created after an automatic update from WordPress account or after an installation of new plugin in your WordPress account. Well you should not be afraid of it can be corrected within 2 minutes with some simple steps.
First, you should try with Plugins:- Most of the time plugins are the main culprits after an upgrade. a simple way to check if any plugin is the trouble maker is to do following steps:
1). Rename your "Plugins" folder and then give a try to check your wp-login page. If it works then you will get the answer that one of your plugin is creating problem.
2). Due to above step all your plugin will get disabled. Now you have to manually enable your plugins and check for the one who will give "fatal error" and upgrade it or simply remove it and try with any other one.
If you find no changes after renaming plugin folder then you should try the second one.
Second, you should check your wp-config.php file. You have Scroll to the last part of your wp-config file and check that there is no extra space after the closing “?>” tag.
If there is a space, delete that space and then give a try.