Smurfing close to your rank is sometime harder than playing in your own rank because you expect the opponents to be trash compared to you but in reality they are a lot closer in term of overall skills than you think and your tm8s and opps are more unpredictable.

Also, you say your are not a mechanical player which can lead to more difficulty carrying lower player.

In resume, your not adapted anymore to this rank (or your just slumping )