ZM

I like the appearance of the potting medium, but those plants sure look like they've been watered too frequently. Lack of any nutritional resources also really compromise development. I hope that we receive more information from cugal.

Started these from seed in 72 cells using ProMix BX, potted up to 32 cell using Fafard's 3B. Those were just watered when pic was taken. I have other flats of these that look fine. I agree (by appearance) they look over watered......... After potting up, I started them on a diluted solution of Jack's 20-20-20 @ a rate of 200 ppm. I've always planted out from the 32 cells they're in.......

Jack's 20-20-20 has almost all of its nitrogen as urea, which is not an appropriate form for use in sterile growing media, because the sterile media lack the microbes necessary to break the urea down into usable ammonium or nitrate forms. Repeated use of urea in those conditions can cause the urea to build up to toxic levels in the growing medium. Jack's 20-20-20 would be an excellent foliar feed, because urea is readily taken up by leaves, and it has a good trace element formula, better than Miracle-Gro (which lacks Molybdenum). And Jack's 20-20-20 would be an excellent drench for garden soil.

I use several urea-free nutrient products for my indoor gardening. Mainly Better-Gro Orchid Plus and Better-Gro Orchid Bloom Booster formula. Several years ago, when I heard that Peters was discontinuing their African Violet formula (also a complete urea-free formulation at that time), I "stocked up" on several packages (actually, all that was left at our local garden/greenhouse store) and I am still using some of that. It may be that some plants can assimilate urea through their roots, but none that I grow.

Calcium is the fourth most needed mineral plant nutrient right after Nitrogen, Phosphorous, and Potassium. It is a macronutrient rather than a micronutrient. And yet soluble nutrient formulas almost never have it. When I began to see distinctive calcium deficiency symptoms in my indoor zinnias, peppers, eggplants, and tomatoes, I obtained a supply of Calcium Nitrate from a hydroponics supply house, and I always include some of that in my indoor nutrient solutions. Pro-Mix contains some calcium, but only enough for a very few weeks. If it is any consolation, your pictures don't show calcium deficiency symptoms.

ZM
(not associated with any product or vendor mentioned or linked)

"That said, my failing Magellans have the appearance of fertilizer burn."

The necrotic lower leaves are a common symptom of nitrogen deficiency. Other nutrient deficiencies (potassium, magnesium, etc.) can affect the lower leaves, but yours look like nitrogen deficiency. It is also possible there are some toxicity symptoms, but except possibly for urea, 200ppm should not lead to toxicities in the time frame your plants indicate. Unless there is something really "wonky" about your water supply.

You said that you were applying Jack's 20-20-20 @ a rate of 200 ppm. That is the same as 200 milligrams per liter. That should not cause fertilizer burn. Can you say exactly how you made up the nutrient solution, assuming that you did not weigh out 200 milligrams and add that to a liter of water?

I usually add a volumetric amount of granular nutrient product to a gallon of water. We have a lot of empty gallon jugs, so it is very convenient for me to add a level teaspoon of nutrient per gallon of water for an initial "strong" dose to add to a pot at potting up time, and then use 1/2 teaspoon or even 1/4 teaspoon of nutrients per gallon for maintenance feedings.

"I've used Jack's in the past on my transplants without issue & some of the current flats of Magellans seem fine. All have had the same irrigation/fert......."

It's possible you have some microbes in some of your medium. A very small amount of garden soil or compost could provide some random inoculation.

ZM

Wonky might well describe my tap water........ It's measuring 500 ppm (cold water) from the tap. I'm told that's a crazy high number for tap water. On city water here...........

So, if your city water is 500 ppm and you are adding 200 ppm of 20-20-20, do you just add the Jack's until the TDS meter reads 700 ppm? Also, have you made pH measurements? If your city water is both chlorinated and fluoridated, your plants may not be liking that. I am still curious how much Jack's 20-20-20, teaspoon-wise, gets added to a gallon of water.

ZM

You have quite a bit riding on the accuracy of your TDS meter. Did it come with a supply of standardized solutions to calibrate it with?

Since a large majority of the "nutrients" in your solutions come in the city tap water, you might want to check with your Water Department for an analysis sheet for their water. They should have one on file, and possibly on their website. At 500 ppm, your plain city tap water could cause "fertilizer burn" with repetitive use.

Or, at least, repetitive use of the tap water could cause toxicity symptoms for some components of the water. I'm thinking about the fluoride, for one thing. But there are other possibilities. On the bright side, your city water may supply all the calcium your plants need.

ZM

"Appears to be very accurate..."

Good to hear. That city water analysis sheet could be relevant. In addition to supplying calcium, your city water might be supplying magnesium and iron. And then your water might be picking up a little copper from the in-house plumbing.

The big seedling in the bottom picture, lower right, has symptoms that I don't quite recognize. The bleached-out color could be an iron deficiency, but based on Jack's 20-20-20 having some iron, and your water supply possibly adding some iron to that, that doesn't seem likely. High pH can make iron unavailable, but the chelated iron in Jack's should defeat that. The purple veins suggest phosphorous deficiency, but your seedlings aren't at the stage where they would need much phosphorous, and Jack's should be supplying that.

So that seedling is a bit of a mystery. It may be suffering from an excess of something. Every problem isn't always a deficiency. That city water analysis sheet could have a clue about something that may be in excess.

ZM