Hmmm. Well, the HP CDRs should be fine at the speeds I mentioned, the Staples DVD-Rs I would be a little more suspicious of.
Can you download and run CD-DVD Speed, put one of the CDRs into your drive, and go to the “Disc Info” tab - then post what it says for Manufacturer.
Then do the same with one of the Staples DVD-Rs, except this time I’d like to see the MID info.
That will tell us who made the discs.
Meanwhile, do you have a copy of any other software you can use, e.g Nero? I ask because it may be easier to control the burn speed with another software.