Yes, and also remember that a TDS meter measures soluble and insoluble organics in the water.
To alleviate dosing questions, I've found that dosing the RO water coming in is easier to calculate. If you have a 4 liter bucket, dose the 4L bucket of RO with your GH minerals and fertilizer. This way, no matter the amount changed, you maintain your target ppm in the tank. If I have a tank with a GH of 5 degrees and KH of 2 degrees, I dose the RO storage to those parameters. I can change any amount of water while keeping the exact numbers inside the aquarium.
TDS meters are incredibly powerful when you know what you are dosing. I dose my 0 TDS RO water to 85ppm, that a ratio of Ca and Mg that's about 4.5 to 5 degrees GH. Many times I will get distracted and forget if I dosed. If I drop my TDS meter in, see 85ppm, I know I dosed it correctly. You can do the same for the fertilizer also. After the RO water is fully dosed, that ppm should be recorded. Do the water change and the tank TDS should be close to the ppm of the new water coming in. If suddenly you test the tank, and see a TDS much higher or lower, you know something is wrong and you can take measure to correct the problem.
Disclaimer: I typed this before having coffee.