Potassium Deficiency?

[Corbidorbidoodle]

Would y'all mind taking a look at my plants to help me diagnose what's going on? I'm thinking Potassium Deficiency. A couple weeks ago, I raised the light a few inches to get better coverage. The Val was growing better before, but this doesn't look like a light deficiency to me.

Parameters...

Ph 6.8, buffer 80, hardness 300+, nitrite 0, nitrate 25-ish, about 14 hrs of lower light (Aquaneat 30" about 4 inches above) 

I use Easy Root Tabs, and I'm pretty sure I've dosed them recently. I've been doing Easy Green twice a week.

Some of the pics make the Val look yellow, but they're bright green. (Potassium Deficiency should be yellow around the holes, right?) The Java Fern has yellow spots though.

Also, I meant to put this in the plants room. How do I move a post?

[Fish Folk]

First of all, that is a beautiful aquarium! Really like your design and fish selection. Well done.

Here are a couple of standard cheat-sheet charts folks use to try to figure problems like these out...

I can see why you're thinking potassium deficiency. Your fertilizer dosing and use of root tabs would be first suggestions I'd make. Sometimes plants are not happy with certain substrates. I've always found that Valisneria struggles in warm tanks, but explodes in my cool water tanks.

It's grumpy in my 83-85 F Discus tank...

But adores my temperate 68-75 F Rainbow Shiner tank...

I think, in general, that softer water has certain problems that harder water bypasses by just providing nutrients naturally with water changes. I use Flourish Excell on this 29 gal tank. No root tabs. I use both a 5000-K LED Shop light, and a plant-growth designed Fluorescent bulb for lighting.

I think that cooler water also holds more gasses, allowing for easier plant (and fish) respiration.