what does 6-4-4 stand for when using fox farms nutrients.?

Same as it does for any fertilizer. Nitrogen-phosphorus-potassium, with the numbers indicating the relative percentages of each. http://www.buzzle.com/articles/fertilizer-ingredie...

Nice web site explaining numbers. You realize only 14% of the plant food is actual fertilizer (minus the micro nutrients which might add another 1-2%). For an organic plant food, this is actually pretty good. The fairly even % across the board would make it suitable for flowering plants. I would not use two fertilizers together as you'd be doubling up the total nutrients used at one time. Not safe. Too much will burn the plants. You can alternate, one time use one, next time use the other. Trust me, they aren't that much different, just good advertising so you bought both.

A higher first number, nitrogen,..is a fertilizer for lawns,..or promotes pretty dark green vines, or dark green leaves...

"can i use em all at once"

No,... just use one type , and less is better, till you know how much is okay..sprinkle fertilizer,..no Piles..