Hi Sendhelp77,
Before downgrading your iCloud+ storage, it is always recommended to archive or make copies of your data following the guidance in Archive or make copies of the information you store in iCloud - Apple Support. This is to ensure that you do not lose access to that data once your iCloud+ storage no longer provides enough storage for all of your data.
If you did not do this, iCloud will hold certain data, like pictures, for 30 days. After that, data will begin to be deleted from iCloud. Even if you sign back up for an iCloud+ storage plan that would cover the data again, there is no way to recover it if it has been longer than 30 days and you did not create an alternate backup.
This is because for certain iCloud features, like iCloud Photos, iCloud is a sync service to make your content available across all devices and is not a cloud-based storage service. Even if it was a cloud-based storage service, if you are no longer paying for that service it is possible you will lose your data.
That said, when iCloud Photos is not enabled your photos are included as part of a device backup. If you created a backup while iCloud Photos was disabled you may be able to get some, if not all, of your photos back by restoring the backup: Restore your iPhone, iPad, or iPod touch from a backup - Apple Support. This step will remove everything currently on the device and replace it with only what was on it at the time of the backup, so we suggest making a current backup first: How to back up your iPhone, iPad, and iPod touch - Apple Support
Best.
