Advice please re problem earrings

[bookbook]

Not sure if this is the right place to ask, but here goes.
I bought my DD some earrings for her birthday, 3 years ago. These were from a highly regarded , expensive, but local jewellers.
They are rose gold ,pear shape which surround pink morganite stones. Not a lot of money in jewellery terms (£150).
I noticed my DD wearing them a couple of days ago, and at first thought the stone had fallen out, but no. They are now greyish and cloudy looking.
I still had the receipt, so took them back today. They told me they were just dirty, and would clean. When my DH begged to differ, they offered to do an ultrasound clean., though the manager was rather rude, and said they would clean up to pink again.Went back after half an hour, and yes, they were cleaner, but still not the lovely pink the stones had been. They have now offered to send them off to be 'steam cleaned '.
Does this sound wrong ?
And more importantly, do we have a leg to stand on if we do properly complain?

anyone?

Morganite is from the beryl family and they attract oils so do go cloudy easily. They should clean up well though so give the jewellery shop a chance to do their best.

Almost all morganite is heat treated (enhanced) to get the pure pink colour but this is a stable process and unlikely to revert.

Let them be steam cleaned and go from there.

Thank you!
We were worried that we had been sold something fake, ( unlikely I know ), as we have never seen a stone 'lose' its colour before.