Unfortunately you are being visited by the oxidation demon. This is a common problem with this style in particular. Oxidation occurs when oxygen comes in contact with your beer any time after pitching your yeast(and according to many, even before- see hot side oxidation)
When you dry hop, double dry hop, transfer to secondary, bottle, these are all opportunities for oxygen to interact and ruin your beer. The early dry hopping produces polyphenols that are particularly felt to be prone to oxidation and ultra short shelf life of these beers. Even careful bottling technique can be prone to this, as I bottled 3 batches in 2015, and all but one exhibited some degree of oxidation.
These beers when oxidized will take on a brown or even purplish color.