We have had no change in the structure of the base support of HP5+ sheet film, nor in its coating ( its coated front and back ).
If you have a standard processing procedure it should always look the same.
A common cause of 'matting' is water held deposits ( hard water areas typically ) or remnants of photoflo, I obviously cannot say this is the cause as I have not seen the neg(s). Typically the emulsion side of the neg should be matt and the reverse glossy.
If you have any concern you can send an example of the film to us to our technical service at Mobberley in the UK and they will examine your film and reply to you.
Simon ILFORD Photo / HARMAN technology Limited :