Can amps cause grounding issues?

yes. does your blues deluxe have a two-way power switch (on-off-on) to select grounding polarity? if so, try using the opposite "on" position.

Do any of the modern (post 70's) tube amps still have a polarity switch? Even on the older ones that do many of those are converted over to polarized 3 prong plugs and the old polarity switch turned over to some other duty.

Are you using a two prong plug or a "cheater" adapter to connect to an older two prong outlet? Is your outlet wired right (polarity correct - line and neutral, ground connected, etc)? You can get a cheap little outlet tester for not much money at any decent hardware store.

Do any of the modern (post 70's) tube amps still have a polarity switch? Even on the older ones that do many of those are converted over to polarized 3 prong plugs and the old polarity switch turned over to some other duty.

good Q. I haven't paid attention to this, though they would not mutually have to be exclusive features. 3rd prong (earth-to-chassis ground) is for safety and might improve shielding -- polarity switch to choose output of polarity of power transformer and is for hum reduction (not safety).
Are you using a two prong plug or a "cheater" adapter to connect to an older two prong outlet? Is your outlet wired right (polarity correct - line and neutral, ground connected, etc)? You can get a cheap little outlet tester for not much money at any decent hardware store.

+1 on both of these. forgot to move them from mind to keyboard.

yes. does your blues deluxe have a two-way power switch (on-off-on) to select grounding polarity? if so, try using the opposite "on" position.

This amp is fairly new. It just has the standard standby/off switch and the on/off switch. I had this amp shipped to me, could it be loose ground wires in the amp? I don't know much about amp wiring. Thanks guys!

I love the way it sounds, but the only problem i'm having with it is none of my guitars sound grounded with it. When I touch anything metal on the guitars it grounds it.
When you touch the strings you are not grounding anything - you are a horrible ground connection. What is happening is that you are being grounded and any noise that you are reradiating into the environment is now being directed to ground through the guitar's string ground. Good description of this here.

I'm sure you guys are getting tired of grounding or earthing questions, but I've got another one for you guys! Ok, I just got a new Fender Blues Deluxe tube amp.
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I have another amp too which is a Vox Valvetronix (solidstate) amp and when I play my guitars with the vox, everything is grounded. Any sugguestions on what might be going on? Thanks!
A lot of (all?) the digital amps have a noise gate on them that will cut off the sound below a certain volume. It may be that you are getting noise with the Vox but the noise gate is cutting it off so you don't hear it. The tube amp doesn't have a noise gate so that with it you hear the noise. What kind of noise do you get from the Blues Deluxe if you disconnect your guitar and the cable? Does the hiss go away (or at least drop)? Almost all tube amps have some hiss so it won't likely drop to zero.