Inconsistent 18ct gold plating. help!

Attachment 13217

Hello,
I have been going to platers near Hatton garden for a year or so to get my sterling silver pieces plated.
I have always asked for 18ct Gold, 2.5 microns.

The jobs I have had done at the beginning of the year look very different from the ones I am getting now. The piece on the left was done back in January and the right was done this month. He has ensured me that they are both 18ct gold plated.
Is this just the usual scenario with gold plating that is hard to achieve a consistent colour?
How can I make sure I get the same colour each time?
Is it something to do with my finishing or something to do with the platers and their processes?

I have been finishing/ polishing the pieces at a higher level than before but does that affect the colour in such a strong way?
Any help and no how would be greatly appreciated.
Thanks!

Have you asked your plater if they can shed any light on why they might differ?
Might be a change in their process, for example.
A consistent process (from polishing on, with monitoring of chemistry) should produce very similar results.