iCloud Photos - Low Qualiry

Hello,

I have recently tried to order some poster prints and I have ran into an issue with low resolution photos.

I have an iPhone 11 Pro with an iCloud plan (100gb). Within photos I have optimise storage turned on so my device stores the low quality photos and in my iCloud should be high quality. iCloud settings are setup to sync my photos across devices.

i have just downloaded some photos from my iCloud and they are downloading at 500kb - too low to print. I’ve gone back further in time on my iCloud and they use to be 5mb which are fine.

Any clues to what has gone on and are my photos destroyed permanently?

Thank you,

Conor