I am not the most experienced hoya grower but the first and third photos remind me of spider mite damage and if it is, I would spray it down with soap and water and rinse it well. If you have a magnifying glass, I would try looking for them - they are tiny and usually red. I would also consider cutting off the affected vine. If that didn't work, I would consider completely changing the soil. Finally, I would take cuttings from the healty vines in the event that the problem worsens. Good luck!

Lisa

I was thinking mite damage as well but you rarely see mites on plants that have fuzzy leaves. Still it's worth a closer look and especially pay attention to the undersides of the leaves.
Eriostemmas want very bright light or even full sun so don't be afraid of burning your plant. This does not mean just move it from inside to out in full sun but it really would do better gradually given more light. These plants grow in bright tropical sun in places like New Guinea so they can handle Florida sunshine just fine.

Mike

Here is a link that might be useful: Hoya coronaria on HortLog

To determine if it is mites, take a piece of white paper, put it under a leaf and tap it. If you see tiny colored specs, it's probably mites. If you run your finger over those specs and they smear, it is mites.

I did the paper test to see if anything would fall off. I shook all three leaves and got nothing. The leaves have been that way for a while now. The yellowest one is at the bottom of the vine closer to new growth area. The other leaves are closer to the main plant itself. I have looked on the underside of the leaves and still have found nothing to prove that I have any mites. I'll try gradually giving it more light. Though I have other plants on the same window, both hoya and orchids and two african violets.

Do you think it could be due to not fertilizing it yet at all? Is this the month to do it?

If your African Violet is happy in that window your Eriostemma will be miserable. These really are full sun kinda plants and full tropical sun would fry an African Violet in minutes.
You can feed your plant whenever it is growing and using half the recommended amount of fertilizer on the container makes a safe solution that can be used much more frequently.

Mike

I would hold off on the fertilizing until it is growing again. The only thing I would recommend is some superthrive or vf-11. If I were you I would spray off the plant with a hose because if there are mites, it will push them off. Then, get some of that insecticide soap/fungicide they carry at Lowes and spray the plant. If you have a rooting aquarium, put it in there. I have brought a Hoya Affinis back from the dead in my rooting aquarium.

Michelle

Another check for mites is to take a cottonball, wet it well with rubbing alcohol, and rub the leaf surface (top and bottom). If the cotton winds up with reddish/rusty specks/streaks you have spider mites.

Is this occurring on old leaves or on the newer ones?

I don't think it is mites. The rule with mites is that they attack the newest leaves first. This leaf is an older more matured leaf. VF11 is insufficient fertilizer for this group of hoyas.
Getting back to the adage that not all fertilizers are created equal, I would recommend using Magamp mixed with bonemeal or lime. Do not over apply lime, and if you made the error of growing this in peatmoss, we will need to change this media. Use a mixture of orchid bark, gravel, coral chips and sand. Or just grow this in straight perlite-vermiculite mixture. The small pot size is a wise choice and once this becomes root bound, you can move it up to a larger pot.
This plant responds favorably to high light and high heat. Best grown in a hanging basket not larger than an eight inch size. Be sure to support this heavy plant with good support wires for the basket. I like to use galvanized orchid pot tongs just to make sure.

I think if it was mites they would be all over the leaves. I moved it to a different window where it can get more light. It also looks like it has a new stem starting to pop out. I also put a stick in to hold a stem straight up, the only reason being that is was top heavy otherwise and that way the leaves would get some light. hanging down as it was, it wasn't getting any light at all. If I remember tonight I will take pictures of it in its new home.

I know that the picture is a little dark ( because of my phone).Here it is in its new home.

is it ok to have it supported so that it grows up? would it be ok to just leave it until it can be put in an 8inch hanging pot or should I let it be?

OK, the problem is that it is also in a too large a pot. Is it growing in peat moss?

I didn't have anything smaller(im dead broke)which sucks. Its growing in potting soil mixed with alot of perlite (sp). I let it dry out almost completely before watering again.