First Mix Grow

Your pH WILL change over time. Your plants absorb nutrients and water and remove wastes, the water itself slowly evaporates over time as well. All these things combined make the concentration of your solution fluctuate. While you can measure your overall EC or PPM to gage your concentration, without more advanced equipment you can tell the exact ratios of what's left in your solution. Because of this it's hard to just top off a tank over the long term and it's a good idea to do a full tank change every week or two. You can go longer on smaller plants that don't feed as much but on a big flowering plant do it more often.

I don't understand anything but from what I can see a problem with watering overwatered/underwater