This is my first grow in around 10 years and these plants are about 2 months old. They are in soil in a small cabinet under about 150W of CFL lighting. I have fertilized only 2 or 3 times. The first time was about a month ago using 20-20-20. That is when these problems first started showing up but they were very minor and i didnt think anything of it. I realize now I should've been much more careful with fertilizing. About 2 weeks after that i fed them a mix of quick grow 1-2-5 and 2-0-0 and superthrive. This is when the problems really got bad. I flushed a couple days later. I have been giving them nothing but water ever since, except I added a half dose of superthrive to one watering earlier this week. My PH has been between 6 and 7. About half of my plants are dying and the other half are doing just fine. I'm not sure why some are doing great and others are dying when I've fed and watered them all the same (maybe that's my problem?). Some of the plants are topped/FIM'd. Here are pics of the dying plants. They're still alive but the new growth is coming out yellow and dried out and dead for some of them. Did I badly overfert or what? A couple of them are getting a little better since i've been giving them just water, but 1 or 2 are still showing no healthy new growth. Please excuse me for being a noob, any help and advice will be greatly appriciated. Thanks, //\\nalog
The main problem is that they are very Phosphorus deficient and have been for some time. None of the ferts you're using are high in P. It looks like there may be a heat and/or watering issue there too, but if so then there's too much damage to say for sure. How have you been testing the soil pH?
ive been testing the runoff water with a liquid ph indicator. so should i just add a fertalizer that's high in phosphorus next time i water? any other suggestions?
it's hard to really tell anything by run-off ph. you should be ph'ing in soil at 6.5. if you properly ph "everything" you put in/on the plants, ph should never be an issue. how did you flush? rule of thumb is 3x the pots size. so a 1 gallon container should be flushed with 3 gallons. use a good soil fert and when you switch to flower do the same.
do you think adding fertilizer is a good idea? the problem got much worse last time i fertilized. i dont want to make it any worse, but i agree with jellyman it does look like a phosphorus deficiency. should i just find a fertilizer thats high in P and add it at like 1/4 or 1/2 strength? what fertilizer should i buy?
well, if you did a proper flush, they're gonna get hungry. in soil i like pure blend. are you in a pre-ferted medium?
Make sure to let the soil sit for at least an hour after watering before squeezing some liquid out for pH testing. The liquid that runs out the bottom immediately after watering hasn't had time for its pH to equalize with the soil's. Some good organic solid fertilizers include Bone Meal & High-P Guanos. Both need to either be mixed into the soil for long-term release or made into a tea for manual fertilizations. The Guano makes tea more easily. Fox Farm's Tiger Bloom is a good high-P liquid fertilizer.