Please i need your help! I got a hoya kerrii a year and a half. It had grown so well, but the last 3 months it stopped and became more and more weak With a rubbish consistency, i dont know how to explain. A grayish point appears on the leaf and expands becoming it yellow and falling. It like a bacteria or fungus dry the stems covering them little by little with a yellow/ grayish film I just water it once or twice a week, i live in miami florida, humid and hot, please i need your criteria to treat my plant. Thanks