Tanya,
I remember now, you mentioned getting a bullion made to the dimensions I gave in my videos on the setup I created with the new lid. I think you said it cost something like £75. If this was the first batch you have made with it then do a batch again using the same Chemistry but with your Silvertron electrodes.
The reason I question this is that my new bar cost almost double that. I have no idea if that was good value or if I got ripped off with the cost of it but I was absolutely guaranteed that it was .999 fine silver. If yours was half that cost but came from a reliable source, perhaps the .999 requirement wasn't completely understood by your supplier and the've just given hallmarked silver. (potentially not .999) This is just a thought, I may be totally off track but think about it.
If you go back to basics then you are only changing one thing (the anode). At least then you can categorically rule that out anything else as a possible culprit.
When I'm doing a dilution, I base it on ml. I just prefer the accuracy of it.
To dilute your 320ppm to 20ppm it would be 234ml water / 15ml 320 silver - 15 / 1 (or 15 parts water to 1 part silver).
As I only ever want a quick check and taste the same can be achieved by dividing down so....
234ml / 15ml becomes.....
117ml / 7.5ml can also become....
58.5 / 3.75ml
All will equal a 15 / 1 ratio.
I just weigh the water and draw out the silver with a syringe. Dead quick and always consistent.
Additionally, I'm not sure how you got the dilution to be so clear. It's absolutely the correct colour for 20ppm "as made" but.....
The reason I say this is that gelatine will generally produce a darker colour so even if you dilute it to the correct ratio, it will generally always be darker!
(your silver particles are capped by this time so the light is absorbed differently.
Take a look a this image in my gallery of a 20ppm dilution against 20ppm "as made"
https://www.gemsdalephotography.co.uk/Client/HOS/Private/SilverTron/SilvertronElite/n-RBppw6/i-bhWTzw5/AAlso, I've found making any silver with maltodextrin instead of karo also results in a slightly different tint. I've learned this is just the impact / effect of the different reducing agent.
Hope this helps.