Control+G(Alt+J) selecting multiple instances, but only deleting from one line

Hello,

So I'm not sure what I did / pressed but when selecting multiple instances of something using Control+G(Alt+J), (variable, function, etc) on multiple lines and pressing delete, it only deletes stuff from the first line, and nothing off the other lines. If I write, it writes on all lines, but when I press 'delete' it only deletes off the first line, when I first clicked and started to press Control+G(Alt+J).

Help please?