Mildew forms for 2 reason: Too much water for too long in the air. Too many leaves and branches on the tree and lack of wind to dry them. Yes Bordeaux mixture is classified as organic spray. Today in Commerce it is hard to find Bordeaux mixture here in the USA,but you will find a substitute called cooper sulfate spray,and they say on the container it works just like the original Bordeaux mixture. If you want good results thin branches in the Spring in such a way that a bird like American robin can fly trough the branches without touching them with the wings. If you do that then later in the Summer the leaves will stay on branches.

Any general balanced fertilizer would be fine, like an 8-8-8 or 20-20-20 etc. You can cut them back, but if there is still a good bit of undamaged leaves then I would leave them until new stems appear. It is a vigorous species and if taken care of it will sprout new shoots soon. Tim Chapman

I think kerrii was one of the first Hoyas I got that wasn't a carnosa-related Hoya and I had some trouble with it the first couple of years. It would put on a bit of new growth and look happy, then it would drop a few leaves and be back to where I started. It seems like when it really started to do well for me was when I got my GH, where I keep it on the top shelf getting maximum sun and heat all year long. It gets pretty dry between waterings - it's the one that I always hesitate before watering. If I have any doubts at all about how much moisture there might be in the pot, I wait a few more days. Your zone is pretty close to mine (not sure if you're in northern or southern MO), so if I were you and you have a south window, I'd move it to get more light during the winter months. This will also make it dry out faster in case it's just staying too cool and wet too long. Denise in Omaha

can we rule out weed and feed spray on the lawn??? im wondering about a minor cold event.. that you werent aware of ... nothing to do about that ... other than see what happens ... im also wondering with the temps and rain.. if its not just growing so fast ... that it just hasnt fully pumped out all the leaves ... and all there is to do ... is see what happens ... do you fert this tree ... soooo ... just give it a week or two.. and lets see what happens ....i am not one to over react.. and try to solve problems.. that might not actually exist ... in other words.. dont fix what isnt broke ... ken