Bot spells timing out fast

The past two days when my bots cast buff spells on me they time out within 20 seconds. They start out with the normal 60:00, 100:00, 120:00 etc timers, but within 20 seconds they start flashing and drop down to 00:06 then time out. This keeps my bots in a constant state of "buffing" and then they run out of mana trying to rebuff.