You have greener fingers than myself – I’m still budless! I have also been seeing spotty yellowing of the leaves & have lost some too. I now water from top to bottom like yourself as they are outside in beds but I think (despite the leaf loss) they still look relatively healthy and are growing fresh new leaves which can only be a good sign. My sunflowers are still on the upwards crawl with no sign of buds or flowering ? hopefully something will happen soon! ???