Movement from Night Wearing of Retainer After Invisalign

There are two reason you are seeing such significant movement after your Invisalign treatment. First, it takes on the average from the time that teeth are aligned about 24 months for the gum tissue and bone tissue to reorganize around those teeth. That is why I try my hardest to get all my teeth align within 6 months of a 18-24 month treatment time. That way, with braces on, I have at least 12 months of stabilization holding my teeth with the braces before removal. I then require at least 3months of 24/7 retainer wear and after that night time wear indefinitely.
The problem with Invisalign are the teeth are not completely aligned until the last tray. It is at this point that the final tray should be worn for at least a year to allow the gum tissue and bone tissue to reorganize to these new tooth positions. I have found that most patient do not adhere to this protocol, and thus, significant movement occurs. This is what you are seeing.
The other reason is invisalign does a good job at tipping the top portion of the tooth and a poor job at controlling the root position after the tooth is tip into alignment. Without controlling the root position, stability after treatment is going to be poor. I do not have your initial records, but I am betting that the teeth which are moving the most are the ones that poor root positioning was achieved with invisalign. The only way to truly control root position is to have a physical attachment on the tooth. This enables the orthodontist to control a tooth in three planes of space.
As you can see, as an experienced orthodontist, I am not a fan of Invisalign. I either use traditional braces or lingual (behind the teeth braces).
For you, I would suggest going back to the last three aligners and wearing the third to the last for about four weeks and do the same for the remaining. I would then wear the last aligner for about a year as a retainer. If these are damaged, you can reorder them from Invisalign through your orthodontist.

It takes time after the active treatment for the teeth to settle in. It depends upon the complexity of the case. When youu wear the retainers at night and they are tight that means the teeth are not stable yet. I would recommend going back to fulltime waer and talk to your orthodontist for other options as fixed retainers etc.