Plants seeding

I have been growing medicinal marijuana for a little while now, and have budded plenty of plants with no problems. As soon as it started getting hot all of my plants started to seed. Any ideas on how to prevent this, or has this happened to anyone else?:leaf::clap:
 
We've been battling the spider mites for a long time but haven't been able to completely get rid of them, only lessen the amount of them. The strange thing is that the same thing happened this time of year last year, but all through the winter we had no problems with seeds.
 
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