Hi Nila,
Welcome to JavaRanch!!!
Of course you can take SCJP 6, in fact
you should take SCJP 6.
The difference between the two is very small. But if you didn't pass 5, I can't say how you would go about it in just 1 week.
You will know in which topics you need improvement. I would not tell you to delay it for a long time, but I would tell you not to rush also.
Take your time, study your weaker topics. Give the mocks and see how you are faring. When you start passing in mocks, go for it.
And go for SCJP 6.
Maybe you could wait for the Plus exam as well. Have a look at other posts about the latest exam that sun's planning.