Ph ppm and ec droping dnt know why water level has...

In DWC pH and PPM fluctuation is normal. let's say you start with water with a pH of 7.5 after you add nutes it's at 6.1 and 500 PPM. If your plants takes water and nutrients in the same ratio, those numbers will remain the same (more or less). But if your plants take more water than nutes, then the pH in the reservoir will drop as nutrients are more acidic in nature and now there is relatively less water. Let the pH hit 5.5 and top off with either plain water or a more watered down solution than initially. On the other hand, if your pH is rising, then your plant is taking comparatively more nutrients than water (1st sign that the solution might need to be stronger). Top off with a stronger solution to compensate. If those changes are happening too fast, then your reservoir is too small.