Do you know if they bloom well in this kind of heat in other locations there in Austin? Osteospermum tends to stop blooming here in California when it gets really hot, and bloom best in late winter into late spring, although they can bloom nearly all year long right on the coast. It may just be the heat. Try moving them into morning sun or dappled sun and see if you can keep the flower buds from aborting.

When you potted them on did you also liberate the roots much?

Sometimes it can take a while for roots to venture into new mix so, while they're 'thinking about it', they're living in their old space. It might be worth taking the stronger one out of its pot and checking.

Along with that - if they had been potted up in a peat-base mix then it might look damp on the surface and be dust-dry in the middle.

If you have them in a fairly gritty mix then the root mass can bulk out and collect enough moisture to sustain flowers - which may be why they do better along the coast if the soil happens to be sandy. (Free root run and that cool, damp stratum often found below the dry surface.)

Your osteo's make a better winter plant than summer in Austin. I have seen lots of thrips on their blooms.Our heat is what makes your blooms abort. The plant is usually grown in California and shipped to the Austin Area,there are a few Texas growers growing these over the winter as well.
Art/Austin,Tx