Hi, and welcome to our forum!
The easiest way to find out since you already have the discs: download dvdinfopro from www.dvdinfopro.com
It will tell you the manufacturer of the discs.
All TY DVD+-R discs is made in Japan. I'm not sure but maxell do probably also have a factory in Japan. At least I've a maxell DVD-RAM disc here which is made by maxell in Japan, so there is a big chance that they also manufactures DVD-R discs there.
But why not give dvdinfopro a try and find out for sure?