I've had yoyo sold by petco get to 6 inches - btw petco knowling mixes golden zebra and yoyo so you never know what you are getting unless you can carefully identify them - i ended up with a mix and they were easy to identify after the first year. None of them were runts or small after a year.The loaches are a mystery. I've spent hours going through the less obvious sources/videos to figure it out. There are recurring theories on seriously fish and monster fish keepers multiple species of what's called a Golden Zebra Loach or a hybrid species being traded. Mine look wildly different than wild caught GZ Loaches. They won't ever reach 4".
The tiny one was sickly when I got it, we named him Sneezy when we got him. He's very small, the only one that looks like botia histrionica.
My own personal theory, most fish sold at every Petco/PetSmart are always max out at smaller side of average, and die of old age faster. Would make sense that bulk suppliers selectively breed smaller, faster maturing species. None of the fish I've gotten from there never passed the lower end of "adult size". My leopard gourami is 4", Bleeding Heart Tetra's are all under 2.5". All 5y/o like the loaches.
It is a problem that asia farms has started cross breeding these various fishes (probably to increase the yield) and one is best off with wc - some of these hybrid seem to be quite vicious relative to the wild ones. Still if they were true golden zebra i would be leary mixing them with dwarf cichlid - they are too assertive. As i noted earlier zebra would probably work (no guarantee) as these are much more passive and shy and are likely to avoid conflict at all cost. The clowns - even small are way too active and clumsy for dwarf cichlid (not to mention they get way too large given enough time). My angels have decided to get rest at night to go to the planted side of the tank to sleep since the clowns make too much noise - this is a long term concern but unrelated to your issue. Sort of like mixing pymy cory with dwarf cichild. I beleive it would work and intend to test it next year - because unlike most cory species pymgy seem adaptive in behavior and like to avoid conflict. The larger cory - like loaches; just ignore what is going on around them and never seem to learn - of course some loach species are extremely vicious and will out right attack pretty much anything in their territory but that too is a side matter.