Before recommending a total reset of the device which is the last thing I like to do, since you mention that the problem appeared after installing a different Launcher, I would try 2 things:
1- Go to Settings and the application manager and there locate the app "Touchwiz Home" that is the Launcher of your Samsung and you give to delete cache and data.
You will lose your entire desktop and it will look like when you turned it on (the desktop only).
2-Turn off the mobile and turn on in Recovery mode and from there you do a Wipe cache partition and restart.
To see if this is fixed and that fault is just some conflict that was left with another Launcher and is not anything hardware.
You tell us.
P.d: To enter Recovery mode on your Samsung, turn it on by pressing the Volume +, Power and Home keys