You could try offering a smaller-than-usual sized meal. That sometimes sparks interest in a finicky eaters for me and gets some of mine back onto feed after fasting.
To answer your question, though, this isn't really the right time for them to go off feed. Ordinarily, the males will go off feed during the winter months when breeding season is in full swing. They can breed at any time through the year, though, so if you've got mature males exposed to female pheromones, that could be causing it.