I have two runners that are about 4 years old and never had a problem. This past weekend the pet sitter gave them almost 90 percent (ugh) cracked corn and when I got back Sunday night they were acting strange and didn't come running for their peas. Now they have not eaten for two days and barely stand up anymore. Is there anything I can do? Has this happened before? Needless to say the pet sitter did not follow the explicit instructions and will not be coming back. HELP