Is there a schedule for adding nutrients to your solution? Plants are healthy, about 4 weeks old, first hydroponic grow. When I check the EC of the solution, it doesn't drop. I was expecting it to drop a little bit and having to add some nutrients to bring it back up. Instead, I mix a nutrient solution in a one gallon jug and add a little bit when the water level drops in the reservoir. I've been completely changing the solution once a week. Everything looks ok, but seems a little too easy.
You may be changing your reservoir way too often. What size it it? I just bollock the water in when needed and then adjust the EC by added nutes and testing it to get it where I want it. If the EC rises day by day it is too strong. If the EC falls day by day it's too week. It seems too easy? Lol, it is very easy, it sounds like you are doing it right
When I say "too often" I don't mean anything will come to harm, just that you may be wasting nutes unnecessarily