Hi Grandma Darr, well my first question is what are you using to repot them? Sometimes for a couple weeks after changing soil hey will sulk a little from my experience. So it may be just fine. But are they loosing leaves or turning colors? Also the smaller ones, if they have outgrown the small pots I would move up a pot size. But I typically wait till they outgrow the pot.
For potting soil, I use a bag of orchid dirt( has bark, perilite) and put potting soil and more perilite in mine. They seem to love it!! I'm sure others will help but wanted to give you some ideas to look at.

I second, Teisa's question. What do you mean when you say they are not looking good? I repotted every Hoya I had a couple springs ago, and only a small handful reacted noticeably. (And those were water loving varieties that ended up drying out too fast in the new medium.) Thus, I think Hoyas' reputation for disliking repotting is a little overblown.

I think most people overestimate the pot size appropriate for their Hoyas. Many Hoyas are adapted to growing epiphytically, in the crooks of trees etc, so their above-ground body gets really disproportionate to their below-ground body. So, you just need to use some common sense, and provide enough room for them to support themselves, without putting them in an oversized pot that won't dry out at the pace they desire.

So, I tend to only move my Hoyas up a pot size very slowly, typically when the hoop required to support the vines is upgraded. A 4" pot is an excellent size for quite a while. I have hundreds of Hoyas in 4" pots that are well over a year old. If yours are in 2.5" pots or something like that, then I think it would be okay to bump them to 4" without worrying overmuch. But make sure they are nice bulky plants with many feet of vines before you move to 6" etc.

As far as changing out medium goes.... It seems that Hoya growers aren't changing soil every 6 months, like Gesneriad growers, or even every year. It has to do with the type of medium that is used, and how fast it degrades. So, you have to know the characteristics of the medium that you are using, to know how frequently it will need to be replaced... assuming you are flushing it out regularly, etc.

In a nutshell, don't feel pressured to upgrade your little plants' pots, unless they're drying out too fast, and look cramped.

Thank you Teisa and Greedyghost;
I have been using a mixture of 3/2/1 Top soil;
pine bark and perlite and have had good luck with it so far. I get the top soil out side at Lowes and I use it as a mixture for all outside plants also. If I ever figure out how to send pictures I will send some . This grama isn't up too much on this new technology stuff. Happy Hoying ! grmadarr