Unfortunately, maintaining a planted tank and taking a vacation are somewhat incompatible. I suspect you just demonstrated that. Snails are natural, and once you have a few you will soon have a lot if there is enough food for them. They do little harm though. Cherry shrimp aren't much different - if you have a few, and they aren't being eaten by the fish, you will soon have a lot. They, too, do little harm. I suspect the pleco went on a flying expedition - search carefully around the floor, under the stand, etc. to find his final destination. The danio is in heaven, as far as a food supply goes, so finding him overfed isn't surprising.
This would be a good time to rescape the tank, and perhaps add a few more fish.