Is this firescale/firestain, or something else?

Hi all. I know you get a lot of questions about firestain, so apologies for adding one more. Thing is I'm not sure if that's actually my problem here.

I focus on designing and marketing my pieces, leaving the casting and finishing/plating to pros in Birmingham's Jewellery Quarter. I'd appreciate your advice on challenging them on some work I'm not happy with (see attached photos).

All the finished pieces in the photos are:

• Cast in so called "Reduced Fire Stain" 925 Sterling (note this is not Argentium silver)
• Not soldered at all
• 1-micron plated in either black rhodium or 18k gold

Are those spots and blotches firestain? Coming through the plating??

Extra thanks for any suggestions on them avoiding this in future :)

A standard method of working around firestain on silver is to plate over it. It's sub-surface copper oxide that's really only seen when you polish down to it (and the high reflectivity of silver can mask it at that stage - until you notice it). It can't migrate through a plating layer.
Those look more like issues with plating - might be a contaminated wash bath, for example. I'd go back to your platers and ask them for advice. On the offchance, have you tried using a polishing cloth on the marks?

Thanks Peter. I did think plating was used to cover firestain, hence why I was wondering if this was something else.

I've polished them with various types of cloth, nothing seems to help. And these are from different batches - so if there's contamination this is a recurring problem.

Appreciate the help. The more I learn about goldsmithing, the more I realise I don't know.