This is my first grow and I am messing it up pretty good. I've made almost every mistake you can think of so far. Read on man. It's bad.
My seeds germinated fine. I transplanted them into a soil that I mixed myself with organic potting soil from home depot, pearlite, and peat. First I didn't have the lights low enough and they stretched. Moved to a few inches away from the 900w LED. Made the classic rookie mistake of overwatering. Got fungus gnats. Got rid of them using food grade Diatomaceous earth. Repotted them deeper to encourage more root growth and let medium dry out a bit. Temp is 77 with the use of a heater and RH is 60%. Running a box fan on low and a programmable humidifier. They are in a grow room that I created, which has no exhaust/ ventilation until this weekend. I'm trying to PH my water to 5.5, but it ends up at about 5.7.
My questions are: The bottom leaves are yellowing and I have very slow growth. What caused it and can I fix it? Seeds are expensive and I can't afford this chit. If it's the soil (I don't have a soil PH tester), can I change it out or is it too late for that? I'm not going to stress them out more than I have and I need to save them. I'm truly medical and can't afford to buy at the dispensary any more.
The pic I'm attaching is from a plant germ'd on 1/15, planted on 1/17. Today is 1/29. This is the only plant that is yellowing, but they all have stunted growth. Please tell me they are salvageable.