Had this problem before. Remix a new batch of soil and repot. You can, in a sense, "start over" and only lose minimal grow time with your cannabis. Peat moss is a good potting medium, but should be used sparingly for cannabis (30% peat max). Cannabis is a voracious nutrient consumer of all sorts of compounds, and peat moss goes acidic rapidly. Combine these 2 facts, and your soil will go to shit in no time. If you are fertilozing these little plants (which I assume are clones), then the problem multiplies.
Just because the first inch of your soil tested under 7 PH doesnt mean the rest is ok (7 is just about the limit of safe soil anyway). You have new growth, and the leaves are the correct shade of green. Sounds like you can take this opportunity and move to a bigger pot. Mix new soil, and use quality organic potting soil, or soiless mix. Potting soil has peat moss in it, so dont add more. Instead, add 2 parts potting soil, 1 part perlite. The soil will hold nutrients and water, and the perlite will allow for oxygen penetration to the roots. Oh, and another tip- use clay (the ubiquitous orange/brown) pots. The pot is porous and will aid in drainage and oxygenation significantly. If you use soiless mix, just add 20% or potting soil. I find that soiless mix works great, but dries out like a sonuvabitch.
Last thing- when your plants are under 12" tall, your fertilizer should be at 25% strength MAX. Those babies dont have the root mass to suck up lots of nutes, so the unused fert just hangs in the soil and turns to "salt." after they get 12"+, then you can add full strength fert every 3rd watering.
Hope this helps!
