First Mephisto Grow

You shouldn't really be seeing a K deficiency in veg but your ratios would suggest it is K. I'm not great at math but as a general rule you need 1.5 more K versus N in veg. So 3 x 4-4-4 + 1 x 2-8-4 would not give you a ratio with sufficient K if you're running a minimum feed. You should definitely find a good PK part 2 before flower hits as that's when you need to keep K levels through the roof. Dual Fuel has the best two parter I've found anywhere, it has a perfect ratio of 0-3-6. The catch is that it only sells as a two parter, you can't buy part 2 just on its own. I make my own PK 3-6 with water soluble Potassium Sulphate, Monosodium Phosphate and Magnesium Sulphate. That's still a work in progress though so I'd be on the look out for a fert that's high in K avg amount of P. Most micros have four times the N a plant needs. I really don't get N deficiencies and how people get them. Calmag also has a bunch of N from calcium nitrate.