Alright so I recently set up a nano tank a few weeks ago and the plants have been growing nicely. Built in LEDs, sand, no CO2
or Excel, Flourish Tabs added 2 days ago and just bought some Tetra PlantaMin. I'm getting a new leaf from every plant every 5-7 days, however some are a lighter shade of green than the old leaves and the new growth on my cabomba that I added last week looks a little yellow. I looked into it and it looked like either potassium and/or iron deficiency (I read that without potassium, plants can't absorb iron properly) so I went and bought some Tetra PlantaMin because on the bottle it says "Rich in Iron, potassium, manganese and other trace elements" so I thought it would be appropriate. A few old leaves have been turning yellow then brown on a couple plants, so it sounds like it's probably potassium that's lacking, but then I read about nitrogen deficiency and it said the same stuff "in the case of a nitrogen deficiency, new leaves will look pale...". So I did a half dose of the Tetra fertiliser. Do y'all think it's a potassium or iron deficiency? Or could it be low nitrates because the root tabs and this fertiliser don't contain nitrates and phosphates. Should I just wait a week to see how the new growth? I'll try to attach photos of an old leaf that's dying and another one on the new growth of my cabomba. I just turned on the lights so my cabomba is still closed at the tip.
Thank you in advance.