Skip the fish emulsion for now, that stuff is very acidic.
I would try this experiment with one plant. Scratch some lime into to surface and give it a good flush. Like 10 gallons of water at least, pHed a bit over 7. If you’re using dolomite lime it breaks down very slowly, so you’ll need to repeat every week until you see improvement.
There’s another type of lime and other products that may work quicker, but I’ve only used dolomite lime. If you have a hydro store nearby they may have some suggestions. Also check out cannabis growing forums - tons of great growing info there that is very applicable to growing kratom.
just a thought.... get pH measuring paper tape to test the drainage water from your potted kratoms. Test the water's pH, running out of the pot. Over 7.5 pH, too alkaline, add acidifiers like gypsum (sulfates)or ammonium sulfate.
Under 6.0pH, too acidic, add alkalyzers like garden lime. Its tricky to manage pH in potted plants, esp.if I use homemade potting mixes. It seems that once they get into the ground that they are easier to keep happy. Their roots are at a more constant temperature, moisture levels are usually consistent, and pH control seems easier. Here all they need is black kow composted manure and maybe trace elements...
Good luck, and let us all know what you find. 😀
oops, I swung the pH too far the other way...🤔
okay I was able to get around to this today. First I'll mention that I'm on well water and my well water is running at 5.5 pH I checked the soil pH of the plant and it was slightly above that closer to 6 then I checked the run off as suggested and it ended up coming out of the pot at 5.0 ish. So I guess it appears that I need to treat the water prior to getting to the plant or treat the plants on a regular basis. I have irrigation setup so probably treating the plant is my favoured option.
Sounds like lime is the solution. Here’s a quick guide to Calcitic vs Dolomite Lime, it’s geared more to farmers and fields but the principle is the same.
Did you place a lot of oak leaves in the bottom of the pots? Might be worth repotting a couple and see if that helps.