We have all been in situations where resources seem to be scarcer than they should be, but please remember that they cannot disappear on their own and the game will never make purchases on your behalf. Resources are needed to make an upgrade or purchase something, so this is the best place to look for an explanation. Maybe you are upgrading a lock or a trap? If that's not the case, check your Defense Logs, someone may have raided you and stolen some of your resources.