Tbh, you really need one.
An EC/PH pen is a must when using solution nutrients.
You are way to much on the N.. but again. It's very hard to judge without pens
But, if you must. Cut what you are putting in it by half.
You really need these. Without your just blindly adding or taking away from what your plant needs.
50$ and you'll get a decent pen from amazon. DRmeter are okay. But if you want something reliable and will work for yrs to come. Invest in a bluelab multi pen. (Ph/ec,(ppm).
I have the milwaukee pens. If you are going to buy a good solution PH pen. Make sure you buy a storage solution to store your ph pen in as the diode needs to be kept wet. And not with water, it'll make your ph pen last much longer. And more reliable.