Yellow Leaves and Making Potting Soil

Instead of seeking for and purchasing good potting soils for plants, can I simply make a potting soil out of humus, compost (manure), spaghum peat, and vermiculite? Would that be sufficient for the plants during vegetation stage? Would that then allow me to control the nutrients better?

I think I have nute burn in my plants, using a Sta-Green Moisture Max soil ( 0.14 - 0.10 - 0.08 ). Do you think the pics are nute burn? Only the bottom leaves are yellowing.