Mystery plants, anyone know what they could be please

Why is it you think they may not be White Widow? You really can't tell what strain you're growing just by looking at a plant - you can tell if it's a sativa or an indica or sativa-dominant or indica-dominant - but these are obviously autoflowers and that's really all you need to know. What I can recommend, looking at your diary here, is that you cut down on the grow nutes... they're looking very dark green which indicates they're getting too much nitrogen and this could cause a lockout of calcium which they're going to need a lot of during flower. I'd cut the dose by at least half if this was my grow... and then keep an eye out for signs of a calcium deficiency which will show up first as little yellow/brown spots.. Also, I don't see that you're reporting on the pH level that you're maintaining... it should be between 6.0 and 6.5 right now... this is also crucial! And then just a comment relating to YOUR comment about watering... don't water/feed on a strict schedule such as "every 2 days" ... instead, let the plant tell you when it needs something. To do this, you just lift up the pot - if it feels lightweight, it needs something so give it whatever is next be it water or nutes. When you water, give it enough so you are getting at least 10-20% runoff from the bottom of the pot... doing this will help clear out excess nutes/salts that may be building up (which is one cause of a nutrient lockout). Otherwise, they look marvelous and you've done a great job so far! But now that they're in flower, you simply need to adjust a couple of things to adapt to the new stage of growth. You should probably be anticipating harvest in 6-8 weeks - autos don't go as long as photoperiods - but this is just an ESTIMATE... yours might be in flower for 8 weeks or they might be in flower for 13 weeks... you're just going to have to "listen" to them and they'll tell you when it's time.. Good luck!