Dwc help!! Need good advice...

Im running a 6 plant DWC system in an 18 gal. res., under a 400w MH for 18/6. if i am 20 days in to veg. and i have changed out the water every week could i leave the nutes in the system for another week and then change it out, or would this be a problem? Also i am feedin the plants consistently when the lights are on, and let them sit when the lights are off on a dual timer. should i be feeding them on a 30 min time frame 3 times aday, or keep doin what i am doin?? i mean it hasnt hurt them so far, just want another growers opinion on my little dilemma!

Yeah you can leave the nute water in the res and just top off the water whenever you need.

thanx never thought of that. what about feeding should i stay feeding when light is on or should i have it set on shorter periods of time for it?>?

The food is in the water, the plant absorbs what it needs when it wants it.
It grows even when the lights are off.
Are you using a drip system? I'm confused about your setup.

yea thats what i got. a water pump hooked up to a drip system its just tht i planted some plants outside at the same time i planted the ones in the DWC and the plant outside seem to have gotten a thicker stock than the ones in the system and i think it is do to the feeding schedule i have the plants running on cuz the water is constantly running on to the plant when the light are on. is this reason to worry?? or am i trippin??

Yeah, you can't really compare your outdoor to your indoor because the sun is better than any grow light you can get.
I'm not sure about the feeding schedule on a drip. Before my roots hit the water I was hand watering only once a day.
There are plenty of drippers on here, they should be able to help out.