Yeah, I was hoping to move away from Urea, my pH being as high as it is and Urea breaking down to ammonia it's a risk waiting to happen for the fish.
For the level of Urea your dosing I see it being a problem, its not even 1 ppm NO
3. I was dosing urea at much higher weekly levels but was doing little and often, worked out about 100times a week on a custom auto doser.
I was a little concerned about excess potassium obstructing calcium uptake but wasn't sure if I was excercising an abundance of caution. I could always use a mix of Potassium, magnesium and calcium nitrates to avoid excess potassium.
Well I have never heard of anyone posting a issue which was Calcium deficiency related. Plus your tap water probably has plenty of K already, don't think the water company's need to report on the K levels in there water reports- so they don't.
Doing it dry then, That's 0.047g KNO3 per daily dose
Dry dosing works best with nice easy masses of salts, IMO starting at 5 to 10 grams ( one to two teaspoons) When your dosing levels require such small masses 0.047grams they is a higher change of making errors. Much better to make a solution when your adding a at least 5 to 10 grams of a salt minimum, then just dose a least 5 to 10ml per time.
I think I might be slightly overdosing the potassium phosphate, It's getting the equivalent of 2.52g per week. (2.9ppm Potassium and 7.04ppm PO4 [2.3ppm P])
For the level of N your dosing the P level does seem a bit excessive as its at EI levels. As for your concern about the K levels I was never worried about K levels being to high.
Another general tip is to not make fert solutions that last too long. 4 to 6 weeks is ideal in a perfect world, as unless the ferts are made in laboratory conditions the solutions will have spores in it etc which has a higher tendency of being a nice broth for them to multiply in. The longer the fert solution is standing once opened the greater the chances and greater still with DIY fert solutions, yes we can acidify them which helps, but having several litres of fert solution with mold in is a PITA and a waste of ferts.
Dry doing works best in big tanks with EI dosing levels, pre loading ferts after a WC and remineralising RO water