I don't know how big the plecos are.. but maybe move the plecos to the 10 gallon (if they are not too large). Some plecos are noctural. I am not a Geo expert at all.. but I know from breeding apistos that the fry are vulnerable to being attacked at night by other fish.. harder for the parents to guard them.
So maybe the plecos are eating the eggs at night. I know at least some (maybe all) plecos will eat eggs of fish.
In an ideal world, you would just have the breeding pair in there. But the next best thing would be to remove the fish you can. What else is in there besides the plecos.