If you have so many ideas in your head (I know we all do from time to time when it comes to writing), the obvious thing is write or type it down so you can come back to it later. You don't necessarily have to write it in straight away, it will make things look rushed.
Which leads me to my next suggestion, maybe planning a little ahead would help. Like having the next chapter or few chapters already done when you post one up, it would take some of the pressure off you and allow you for more flexibility if you get behind schedule or something like that, especially with 6 fictions if you continue to do them like you are now. And as people have suggested already, quality over quantity is the way to go.
I recommend you focusing on continuing and then finishing off one of your fictions, then going to the next one. Focus on it good, proofread it as much as you can, learn from the critique you get from other people, improve your fiction from that, give yourself one week to do all that and you'll be fine, best post the chapter on a weekend too.
My first fan-fiction on here '
http://anime.myfavoritegames.com/com...all-z-2-a.html- ', is living proof of that, see the unedited episodes.
My attempt to rewrite it '
http://anime.myfavoritegames.com/com...-epidemic.html', now compare these and you can see I went from 'lacking' to 'too much', when it comes to description at least ...
And now I suddenly want to rewrite the fiction yet again, I wonder if I will every finish it ...
Eh, it's not the best example on the forum but I hope I get my point across. And one last word thing, too much description can be bad at times, and might even bore the reader in some special cases. Just my advice to you, from personal experience, though it really depends on who's reading and their personal opinions.