Small Hoya leaves slowly turning yellow
Hello! I am a first time poster, and I read a few other threads on yellow leaves, but even after trying some things I'm still concerned..
I have two hoyas by my window, one is a few years old with lots of vines and dark glossy green leaves with white speckles. The little one was grown from a leaf of the bigger one, and was doing well in a little 4" plastic pot, but about a month ago two leaves started turning yellow at the tips, and the yellow spread until one fell off, and then about a week ago the other fell off after turning all yellow with some brown along one edge.
Now some other leaves are showing yellow near the tips, and all the leaves have been paler and lighter than the parent plant for awhile. I thought perhaps I needed to fertilize, which I'm fairly new to, but I mixed some fairly balanced organic fertilizer into the top of the dirt and watered it, and sprayed the leaves with liquid fish fertilizer, but I haven't seen any change for the positive over the last week, and I don't want to overfertilize... would it take longer to see an improvement if that was the problem?
The leaf that fell off last week:
The other leaves showing yellow:
The little hoya now after a week with fertilizer next to the parent hoya with all leaves not as dark:
I'm hoping/guessing it's not rot since it's been happening so slowly and only a couple leaves at a time.. The leaf from the parent plant is still green too, so if they were just old, wouldn't it be likely to yellow first? Any help would be very welcome! Thank you!