slow growth and salty residue

[ShuttyMcShutShut]

Im on week 2 with 2 white widow seedlings that are planted in a waterfarm. They sprouted super quick and I put them on 24hrs light(400w hps), 85 degrees or lower temp, with 24 hrs watering(bottled spring water, no nutes). The PH kept hanging around 6.2 and going up from there so I kept adding vitagrow PH down....I would have to take the ph down to the high 4's or low 5's in order to keep it from climbing to the high 6's by the next time i checked it. I was checking morning, noon, nite, bed time. The problem is this, my leaves were a light green with slow growth; then a white salty looking residue began to appear on the drip ring for the waterfarm, then the same white salty residue started appearing on the stalk of my tiny seedlings, at closer look that same residue is on the leaves in a much less noticeable presence. My question is this, I tend to want to blame the PH down for being of low quality....ive used it on grows before but never had this problem....even did the exact same grow last year(only with 1 on, 2 off watering cycle). Has anyone seen plants excrete anything like this white salty residue? is it possible that my white widows want the ph at higher than usual and are actually absorbing the PH down? for what its worth, when i adjust the PH, i drain water into a small container, 10 oz or so, and then add a few drops of ph down, stir it, pour it onto the top(trying not to let that water make contact with the plants before it drains down, I then drain more water into the same container and pour it into the top....trying to flush all the super low PH water into the res, i wait a few minutes for the water to adjust and drain more into a different container, and check it with my hanna ph meter(calibrated with 7.0 cal solution). Ive just never had my res water so adamant about being high, ive tried to adjust and its like the plants are filtering out my ph down and that in and of itself is harming the plants, not to mention the HIGH ph that follows. Im sure its not good for them to be absorbing and excreting PH down. Its a new one on me, thats for sure....any suggestions are gladly accepted.
Peace

 

[HippyInEngland]

Check your bottled waters calcium levels.

Have you physically checked the spring waters PH?