Hi Ann!  Yes, if you are tuned a little low (CGC) then the strings will tend to vibrate in a wider arc when picked or plucked.  This would explain why you get the buzz only when picking the string a second time, while it's still vibrating from the previous note.  Three things can help this- 

1) try tuning up one step to DAd and see if it is improved by having more tension in the strings... or,

2) stay in CGC and put on a set of strings that are slightly bigger gauge (instead of a .010 for example, try a .012 or so- this will also add a little tension and decrease the vibration arc of the strings...  and

3) Ken mentioned something about this- try picking with only the very tip of your fingerpick and not the part nearer your fingerpad. It sounds like the already-vibrating string is prematurely hitting the pick right before you actually pick your note.  Playing closer to the pick tip end would help this.

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Site Owner

Those irritated by grain of sand best avoid beach.
-Strumelia proverb c.1990

Try without the picks. I fingerpick most of the time. I like the softer sound produced and I don't get any pick noise. :) It may also help pinpoint the problem.

Ann, I have to agree with Ken that if a given string only buzzes sometimes, then the problem is probably not the string gauge. 

You might ask for help with fingerpicking technique in the Fingerpicking Group here at FOTMD.

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Dusty T., Northern California
Site Moderator

As a musician, you have to keep one foot back in the past and one foot forward into the future.
-- Dizzy Gillespie

Here's the Strothers String Gauge calculator:

http://www.strothers.com/string_choice.html

Plug in your VSL and the open notes of your tuning, and your string gauges should be at least the numbers shown there.

Is the buzz only on the second picking of the same string?  Could it be you're digging deeper/harder on the second pick and making the tring vibrate wildly?  If the buzz isn't an "all the time" thing, then the cause pretty much has to be your technique......