HELP Seedlings trying to DIE yellow leaves with brown spots

[Carri]

Fairly new at this and feminized plants are trying to die. 7 wks and largest is 7" tall in solo cups, holes in bottom and around outside edge for drainage and air. Yellow leaves on bottom started after being in solo cups about 10 days, used CoCo Coir for medium. Bottom leaves started getting yellowish and then got brown spots on them. Not around edges, more in center of leaves. Yellow/gold leaves spreading up plant. Tops look healthy but growing slow I believe, very light green in color. Have them on a heated pad on my bathroom counter to help with humidity as I live fairly northern in US. Initially seedlings loved heated pad kept at 75 degrees. In last 5 days turned pad off as it seemed to be at 80-81 most of the time. Weather here is getting warmer, have windows open. Put plants in window sill of open window during daytime, last 3 out of 5 days, then back under grow lights to finish light hours, doesn't seem to change anything. Stems seem to be strong for the size of the plants. Tried nutrients, seemed to make condition worse. Tried bottled water with minerals, seemed no change, if not worse. Tried plain well water, no change. Have blue spectrum grow lights over, tried 18/6 hours seemed to get worse, put back to 16/8. Humidity now is 55-63%. Last year plants grew pretty well, just a little smaller than would have liked. Does anybody have any idea what I can do to try to save my plants??

[Catfish22]

Without pictures I'm guessing from your description that they may be root bound and need a bigger pot. I presume you were planning to transplant them.

If you go to GWE and search "root bound" and "seedling care" the tutorials will educate you on the subject.

I did not see any mention of pH testing. What are your pH levels running? 🙂🌱

[Carri]

Thank you for your fast response. Tallest seedling 7" but two of them 1.5" and have the same problem, seem to be dying from the bottom up. PH checked one day ago and at that time was 7.5 - 8. Cannot seem to get PH down, any suggestions?

[Tersky]

Growing in coco you need cal mag and nutes as coco has no nutrients. Also, repotting would not be a bad idea although you can grow a plant exclusively in a solo cup but you just wont get as much as you would in a 5 gal pot. Also like Catfish22 said how is your ph? ph for coco should be between 5.5 and 6.5 to prevent nute lockout. I recommend reading the tutorials on the main site as those can tell you everything you need to know.

[Carri]

After looking at tutorials it appears there could be a magnesium deficiency but after giving magnesium nutrient plants do not look any better. They seem so dry, so give them some water (not too much) and the top leaves get lighter green yet. Friend who got me started on this project says "Its a weed for gosh sakes how card can it be?" tried tap water to get Ph down, but did not help that either. Guess transplanting is next step.

[Tersky]

I dont know about your tap but my tap has a ph of like 8 which would not bring ph down. Do you test your ph before adding nutes or water? I grow in coco and always ph my nutes and water to 6.0. If you are not testing and maintaining your ph that is most likely your issue. Also if you are not adding cal mag to your nutes then you could be experiencing lockout due to the coco binding with other nutes making them unavailable to the plant.

[Carri]

Hey Tersky, have been using Aquafina water the last week, which has pH of 4.5 I believe and my pH is still up at 8. Any suggestions how I can bring it down? In checking my little plants daily now there seems to be new little sprouts on stem where brown leaves are falling off and new leaves on top all the time. How can a plant be doing bad and good at the same time?!!Wish I could have sent pictures at the beginning.

[Tersky]

Aquafina has a ph of 4.5? You may want to contact Aquafina cause it sounds like they are selling a weak acid. Either that or your testing equipment is way off. I use PH Up and Down from General hydroponics to regulate my ph.

[Catfish22]

I still believe its rootbound.

[mactheman]

the plant is not very big i's like what Catfish22 as already said its rootbound it should be a lot bigger ,,it really needs potting on to bigger pot ,,,,,mac,

[Rwise]

To raise one in a solo cup is a challenge, it can be done, but I dont think its for me. I am not that good, therefore I use lots of soil.
Did you prepare the coco? I dont use it but have read it needs to be prepped before use.
I would remove all dead growth and replant them deeper in a much bigger pot, with the soil already at the proper PH, or use a living soil (this is what I make and use) that will let the plant control the PH.

[Ace1973]

they are root bound, your ph will never regulate until you transplant into bigger pots. this causes nutrient lockout, which is why leaves are dying.

[DeadlyFruit]

Agree on a bigger pot - usually between 5 and 10 gallons although some go smaller and usually if outdoors many go bigger.

Just to add, because it sounded like you may not be solid on the topic, you should absolutely test the pH of your water after you add the nutrients but before you give it to your plants. Some people will also test the runoff water. If you need to bring the pH down, as most do when using coco, you can add some lemon juice or some other acid to your water (most will buy a bottle of ‘pH Down’ and add a couple ml of this). Stir well and retest to be sure it doesn’t need further adjustment. You may want to let it rest a little and retest. Test with a pH pen rather than paper or drops as the pens are cheap and easy to use while the paper and drops are difficult to read accurately (but remember to learn about calibrating the pen and do so every couple weeks).

Don’t forget your cal mag with the nutes and you are on the road to an improved grow.

[Carri]

Thank you all so much! finally transplanted into a large pot on 6/5, since I did not have gallon containers offhand, and in 3 days time the worst-looking plant in picture 6 grew 4", WOW! I was impressed. Losing brown leaves and plants are so much greener, guess I should have listened. Thank you, thank you, thank you!

[Carri]

Tried solo cups for first time and will not use again!