how big a skill difference is there between the 3.40s and 6.50s?

[burns-1986]

i recently just moved up from 3.40s to 6.50s on stars and my results have suffered a lot. My roi over about 900+ games was 18% at the 3.40s. Since i have moved up my roi is -2% over around 100 games, i guess my question is am i just hitting a downswing at the wrong time or is there really that big a difference in skill?.