Reasons Sun Gold isn't sweet?

[bin4given2]

I've been growing Sun Golds every year for 5 years in a 20 gal. grow bag - they are always sweet and flavorful, but for some reason they are not sweet this year..... at all. I cannot come up with a reason why, unless it is related to the first signs of blight (early, late?) showing on the bottom leaves. Any ideas? Growing season has been good and early this year in Colorado!