Moldy Paint and Art Show

Updated to add: I contacted Sax/School Specialty about my moldy paint. It wasn't old paint, just from earlier this year. They are replacing it! Nice customer service there!
I am in the middle beginning of cleaning up my rom for the year and packing everything for a move to a new, old building. I discovered that both my blue and purple gallons of tempera are moldy. Is there anything I can do about it? Is there something I can do to prevent it next time? I had to work pretty hard to get this paint, so it kind of kills me to just trash it.

The last 6 weeks have been art show season around here. Three art shows for the district, with 15-60 students participating in each show. Tonight was the opening for our school art show. Every student participates, with at least one item, but most have two or even three. SO. MUCH. WORK. But, so worth it. Of our 500 students, there were probably around 100 students there. And still, it was worth it. It was worth choosing all of the work,  labeling it, displaying it, and publicizing it. Worth every darn minute to see kids so excited to show off their work. Parents were proud of the art their students had created and I was proud of all of them, too. I was already talking to my principal about how we can make it even better next year. (#1 priority - earlier in the year, this is seriously ridiculously late. We only have another week and a half of school.)