As far as looking at the trichomes I find my phone zoomed all the way in up close will get a solid picture. When I put it on the PC and zoom in a bit more I can tell between clear, milky, white, and amber in the trichs. My phone is a galaxy s5, so not exactly old or new but it gets the job done.
PH can be a real bastard, I've fought with it before. I've switched to the advanced nutrient sensei grow and bloom a&b and as long as you add the nutes in the right order and mix the solution between adding each one, the PH is always perfect. Can't tell you how much easier and more time saving it is to know your ph is always right. The AN line also grows some pretty bomb plants, though it's also pretty pricey. Tang's got some great easy schedules in the fertilizer section if you're interested, you really don't need that much of the nutrient line to grow some awesome ladies.
Hope you got the nitrogen issue worked out, your plants look pretty healthy otherwise. Even if you didn't correct the issue there's no reason to abandon any girls. I had some serious N deficiency in my last grow and the girls put out some of the frostiest bud I've ever grown, but the yield kind of sucked balls. Good luck man.