The dates of what and when are a bit more complicated than people may think!
Earlier literature has stated such as: "Paul Ysart left Caithness Glass in 1970" and "the Harland works were started in 1971". However, later information sets Paul's retirement from Caithness Glass as "during 1972".
Which means that, depending on whether there was an overlap of both Paul and Peter Holmes making the "stones", we probably should be saying that Caithness Jewellery from 1968 until at least "sometime in 1972 had a py "stone". And we have to allow for the remaining "stones" carried forward from "sometime in 1972". In fact, Colin Mahoney, in his book on PY Paperweights, said, "... much, if not all, of the 1973 pieces contained Ysart canes".
So, for the items in this thread, my thoughts about who may have made them would appear to be even more inaccurate, given the hallmark dates of 1970 and 1971. But I stand by my "sitting on the fence". The 2nd example is not in keeping with my experience of PY "stones" and the 3rd one looks to me as though it might or might not be by PY.