I am still a beginner but I believe that your plants are looking great! It is normal for the fan leaves to turn yellow when your plant enters the flower stage. The plant is focusing on producing big buds, not keeping fan leaves alive. They start to turn yellow because the plant is sucking the nutrients from the leaf and using it for bud production. If you were still in the vegetative growth, then I would worry. But I wouldn't worry now and keep doing what you are doing! If anything clean up the plants a little bit by picking off the leaves that are over 50% yellow or dead.

Your PH is fine I wouldn't stress too much about buying professional PH kit. A lot of growers are picky with their PH, but it seems a little over rated to me. As long as your within a 6-7 range, you should be fine. A quick fix would to fill up a huge container with your tap water. Let the water sit for a couple of days, then water your plants with that. I think it help stabilizes the PH and evaporates salts and other stuff that you don't want. Also 2 weeks before harvest I would flush your soil. You don't want your plants to taste like fertilizers. Using molasses a few days before harvest should be fine though.

As far as a bug problem, it looks like you have thrips. Those little black dots look like thrip poo. They suck nutrients out of your leaves. They also plant their eggs in the leaf and in the soil. You have to spray the soil, just not the plant. Also make sure you get under the leaves sprayed. I would spray in the morning, then follow up a couple of days later with another spray. Make sure you spray any plants near your babies too. My favorite spray is neem oil. You can use that stuff up to a week before harvest and its organic! A good alternative to spraying is buying nematodes and pirate bugs. Maybe plan for that next time around. Also lightly rinsing your plants down in the morning is a good idea. Bugs hate moisture and spraying them will knock them down a little bit. Watch out though because when in the flower stage you don't want too much humidity because it can create a mold problem.

If you want you can feed the plants a little bit of nitrogen. But I would focus feeding the plants with phosphorous and potash (potassium). I use Fox Farm Big Bloom, Fox Farm Tiger Bloom, Molasses every other watering. I might also pick up some Fox Farm Cha Ching. Bat Guano is also good, but watch out with manures because if you use too much you can burn your plants. Try to only use 100% organic fertilizers, it taste better than chemical ferts and less chances of burning your plants.