Consider using a simple manual siphon pump. Have some plastic tubing (the diameter will depend on the opening of the siphon pump) inserted into your jar all the way to the bottom. Let the other end dangle below the jar bottom to a common collection bucket. Do this for each of your jars. When it's time to change out the water use the siphon pump to start the flow going through each of the tubing. Should not be too long before your jars are empty. Now if you really want to get this done fast consider getting a small self priming pump and hit each end of your tubing in succession. You will have emptied your jars in no time.

Maybe it would be easier to set all the jars in a shallow drip pan. Then, just over-flow the glass containers a little bit each day to replenish. If you used something with a flexible tube, you could direct the fresh nutrient to the bottom area of the container while the older mix overflowed to the drip container. I was thinking that perhaps cutting off the bottom 2 inches of a gallon jug might make a convient drip pan for the glass containers to sit in. If your growing chambers are too large for the gallon jug bottoms, perhaps something else from the plastics section of a large department store might work. Maybe a turkey bastor might help out somewhere in the operation to avoid the overflow mess. chuck