Ribbed newt sexing and breeding (sexual maturity)?

Hello everybody, I have 4 ribbed newts, 3 of which are albino and the remaining a wild type. I noticed some of my newts have little pads on their arms which I know are nupital pads, but I'm still confused on breeding them, I also want to be sure which are female and which are male. I see them doing amplexus but it's always random, it's never after a water change like people say and it seems as if they do it at random. When I introduced the black newt, it was courted by one of my other newts, but I can't just buy another newt just to trigger courtship. They are also about 4 inches long, how big do they have to grow until they can breed, and how long would it take for them to get that size? Thanks

Below are a couple images. I think the third one is a male, while they other ones are female

Maybe you'll find some helpful information here.
https://www.caudata.org/cc/species/Pleurodeles/P_waltl.shtml