When do you get preamp distortion ??

If I have my 210HD130 (new tubes, original caps)
set on 3-4 or above on the volume and the master at 7 or so I start getting some OD type distortion when the guitar (carvin with passive humbucker) is around 80% maxed. If I switch to high power then its clean at the same settings.
I keep the volume at about 2 on the preamp when on low power to keep it clean at max guitar volume.
Is this normal or signs a cap job is needed??
Thanks

I ordered the required caps, BTW Newark had all of them in stock.
Question....Old caps have the Pos end marked Correct ?? while new will have the neg end marked ??

Actually, they aren't "marked" but it's easy to tell one end from another. THe ground end lead goes directly into the metal can and the "positive" end has a rubber or plastic insulator. Your caps are probably due and it's cheap insurance.

That makes sense, Thanks Mike

Well.
new caps didnt help this, Per my other post asking for help