My plants are doing good but they keep changing from a healthy green to a pale green.

I have 6 indoor plants in hydro, with a dutch master 2 part veg solution, add.27, and a CO2 bag. They are about 3 week old clones, their leaves of the new growth seem to change from a light green at night to a darker healthy green during the day, plus it seems to start in the middle moving outward. I constantly adjust the PH to keep it ideal within the tank. Other than the color changing the roots are doing awesome and so are the plants. They have grown .75" or more in the last 36 hours. Any help would be appreciated. BTW its my first grow. Thanks for the help and input.

u give co2 during veg? what does it help? i know giveing it to them in flowering will help them withstand higher heat and increses bud mass by up 2 25%.

Its a tight space so the heat is pretty high and the bag helps with the breathing and photosynthesis.

New growth is usually a lighter green are they getting bigger maybe new growth is turning darker while the keep growing new new sites that are a lighter green

The light green/yellowish leaves are just new growth. New leaves don't have as much "green"
(chlorophyll) because the leaf hasn't had a chance to grow its own green yet. Leave them alone
and you'll be fine. If you keep adjusting something every time your plant looks different you are
likely to screw up. If it ain't broke don't fix it.

BigSteve.