Epsom salts (magnesium) in veg, once or twice. I never put this into the soil as it can contribute to salts build up. This is great for a fast 'green up' if things are looking a little pale or yellow. It will correct this within a couple of hours of spraying if it is a true magnesium issue.
Liquid seaweed in veg: makes a good foliar treat occassionally!
Organic Neem oil Veg/early flowering. Lovely stuff but it stinks! I use routinely as a deterent to mites etc, it gunges them up...... top and bottom of all leaf.