Veg+bloom, advanced nutrients sensi, and xnutrients are pretty clear and easy enough to chech ph.
Also, try mixing up several batches at different ph ranges. Do 8.0, 7.0, 6.0, then 5.0. Use shot glasses and line up all your batches side by side so you can compare them. Try it with and without nutrients. Doing this a few times helped me get a feel for how many drops change the ph range. Then it was just a matter of making an educated guess.