The second one, from what I can see of it anyway, appears to be natural. I might change my mind if I seen the other side... but more than likely not. Notice it does have concoidal fracture scars but they are HEAVILY worn, and have a rough bubble like texture not typical of most knapped artifacts, indicating great age... (from before the natives were here I would say) Now with all that being said I will also say that I have on RARE occasion seen artifacts that had spent a great deal of time in an active river system and had heavy wear on the fracture scars as well but the difference between those and this is just a judgement made from experience.
On the first two arrowheads, they look pretty nice- I don't know if there is much I can tell you about them because in terms of how they are attributed to a certain age... well that's kind of geographically related and I'm not overly familiar with texas points but my hunch is that they are at least in the right neighborhood in terms of age. Actually, now that I look at them again I would think that first one is actually a little older than that... but again.. I don't know Texas stuff that well.