Are Rhaena and Baela Bastards?

If Rhaenyra's children are doubted because they look more like the Strong side than Velaryon, then how does Daemon marrying Laena half-Targaryen, result in Baela and Rhaena being fully Velaryon? Meanwhile, Corlys marrying a Targaryen produced mixed looking children. Does that mean Baela and Rhaena could be bastards? Why are their parentage not under doubt?