There is no way to tell which species of cory or other fish these eggs are, they all tend to look much alike except perhaps in size. But corys do place their eggs on surfaces, and if they are the only fish in the tank, these eggs must be theirs. Loricariids also lay eggs like this, some species on vertical surfaces, some in caves, under leaves, etc.
The eggs will darken as they develop. Corys often spawn over a long period, even days, plus you could have eggs from different females. External factors (the weather, water changes) can trigger spawning and all of the corys might well do it at the same time.
If there are no other fish in the tank, the eggs may escape predation and hatch. Corys themselves are not that bad at eating their eggs, but other fish easily do. Once they hatch, they will need microscopic food. This will be available on the substrate, among plants, on wood, if the tank is not new. Adding dried leaves (oak, maple, beech, generally hardwoods) is very beneficial to provide infusoria and bacteria. By dried I mean the leaves have fallen from the tree and are completely dead and dry. You can get into other foods, but I go with what I've suggested. It won't take long before the fry discover sinking foods that the adults eat, like pellets, tabs, disks. Provided there are no fish (aside from the corys themselves) you should have several survive.
Byron.