The problem with any rainbow is if it's not entirely upped it will have a much larger increase in loss when versusing FGs. It's good you have Pulvy and some green shards upped, but you'd need at least 6 Supernovas before you can start to look at rainbows as an option. Though there are rainbows that can run FGs without upped SNs, it's much better to have them as they dramatically speed up a rainbow.
As for the Pesty FG killer, the deck is dependant on getting to your pests fast and dumping them out as fast as possible and many FGs can out rush the pesty fractal. A few, like Rainbow and Chaos Lord will run SNs as well, making pests almost worthless. Pesty is great for some FGs, like paradox or osiris who require certain quanta types that can be zeroed out by the pests, but again it's a race to the fractal to get to a bit of a lock. And if you're like me, the stoopid Dusk shield works 90% for the AI and 20% for me (I know, I know, it doesn't REALLY work that way, but it sure as heck feels like it!).
All in all, I'd say you may just be experiencing a down time with the deck as it does work. Maybe it's just bad luck with getting certain FGs, but if you want to upgrade to an upped rainbow, you're either going to have to tough it out with Pesty vs. FGs or run a T50 deck so you can build up electrum. Once you get some more upped, and go with CCYB for instance as far as rainbows go versus FG, your luck should improve.
