What to feed french climbing beans & onions

They don't really need feeding til the onions are bulbing up and the beans are showing signs of emerging beans.   Beans are heavy feeders and would benefit from some muck round their feet. I like natural food like comfrey tea or seaweed liquid but you can use stuff from Wilko etc like Phostregen or Miracle Gro

Dad is wanting to know what to feed these on to make them better! Help will be appreciated for him. His first time growing these.

Thank you

high nitrogen feed up until the longest day (mid june).then switch to a high potash feed to bulk the bulbs out.bob