Cannot login to ftp user account, cannot change password

[ppaustia]

I am able to log in and to upload ftp files using filezilla and my primary account
But when I create an ftp user, and try using filezilla with that, I get a 530 Login authentication failed error. I've tried creating several ftp users and I get the same error with each.
Then, if I try to edit an ftp user (to change password or disk quota) the "Save Changes" button does not do anything. I've tried it on several different browsers (Chrome, Firefox, Edge, IE), nothing. I've tried different passwords, in case it wasn't long enough or used the wrong characters, still nothing.
I'm also wondering why each ftp user I create shows that it is using a different amount of disk usage even though I've never successfully logged in to any of the individual users, only to my main account. I'd probably delete the ftp users, but when it tells me one of them is using 42 Mb of disk usage, and another 13 Mb, while my default account has 30 Mb, I have no idea what I would be deleting.

 

[Anna]

All ftp accounts that are created within your account does have a username in the form of user@yourdomain.x10host.com (the default being the exception as it is your cPanel name that is already unique for the server), are you putting in the full username or just the part that comes before @?

What the cPanel is listing them as using is what the contents of the folder you give them access to adds up to

 

[ppaustia]

I have been using the full user@yourdomain.x10host.com username.
Is there a reason why an ftp user I created would have access to 12 Mb more disk usage than what my administrative account has access to, when I've never even logged on as that ftp user?
And if I simply delete the ftp users, (I don't really need them and I'd rather not have them at all than have unusable and perhaps faulty gateways into my files), will I be deleting any files that I might actually need?