Another thing to check. Your blanket wash can actually cause foaming in your fount tank. If you have just perhaps, changed your blanket wash brand, especially if using a water miscible wash, the wash feedback to your chiller can cause foaming. Water miscible washes have a surfactant in them that allows water to temporarily mix with the wash. These surfactants are like a soap, and as such, can cause foaming. The same holds true for some plate cleaners.
To check, get a clear plastic (personal size, not a drum) water bottle. Fill it half full with freshly mixed fountain solution. put a few drops of your wash into it, and shake it vigorously. There may be some foam appear, but it should almost imediately dissapear. you can try this with plate cleaners, mrc's, etc. If you happen upon a combination, where the foam will not dissipate within 5 seconds or so, then youve likely found the cause of your foaming. ;-)