Ppm

If your ppm stays around the same in your tank it could means that the plants needs are low so she is not using many nutrients so no need to push her. If you filled a tank with a 1.50 ec value and after a week your value goes down to 1.40 then your plant did only "eat" 0.10 ec so no need to worry or to hurry If you means that you have the same EC since 2 weeks and you would like to push it to see the result I feel like if your plants have no issue with the 1.49 dosage you can try an higher one and monitor your plant to see how she is reacting to that change , if the reaction is negative then get back to the old value and try to wait one more week before increasing the dosage