Hi Terra
It looks from your screenshot that only some grades are locked (although it is not sure if this screen is the gradebook or the assignment submission screen. I will assume this is the assignment submission screen as this is the most common place I see this!
When grades are entered directly into the gradebook the score and comments entered 'lock' the data entry via the assignment. If you'd like to alter these grades then you need to go back to the gradebook at alter them there. If you'd like to enter the grades/comments for these students via the assignment submission you'll need to edit the individual grades (click the edit icon when editing is on in the grader report) and untick the 'Overridden' checkbox field.
If you are viewing this via the gradebook then you should click the closed padlock with editing on to unlock the grades. If you cannot see the padlock icon then click the 'My Preferences' tab and ensure you toggle the relevant icons so 'Show locks' is set to "show".
I hope this helps
Cheers
Teresa