Similar to @henning's good answer, but emphasizing a way of thinking about such things: be forthright/honest. That is, you did literally learn of  and  from the secondary source, so it would be helpful to your readers (and factually accurate) to acknowledge this source, as secondary as it may be. That is, you help your readers by explaining the helpful sources you have found. Still, in terms of "primary facts", also  and  should be cited, for somewhat different reasons.
That is, I think the best (certainly the most honest) scholarship admits what sources were used, how one found things, and so on. To do the opposite, that is, to pretend that one only ever consults "primary sources", is fairly ridiculous, even if it is a popular style. In my field, mathematics, in some cases the original sources are quite inaccessible or anachronistic/archaic, in various senses. So I cannot trust myself to read them with understanding, even if I can acquire a copy. So I must trust others' rewriting, explication, paraphrase, etc. But/and I should acknowledge the historical antecedents even if I cannot directly benefit from them, and also acknowledge accessible/intelligible "secondary" (often with much "value added") sources also.