It is very common in autos to get 3 leaves during flowering. As @HarbingerofHarvest mentioned. Leaf blade count is based on hormones. The rapid changes of autoflowers and their nature. Leaves them doing too much at once to produce high amounts of this hormone.
Ok im gonna try a 20/4 lighting pattern and i recived a ph tester but awaiting batteries as they didnt vome with it ... ive ordered ph up and down aswell so hopefully will fix it.. thanks for your comments
Looking at your diary you have a ph problem..in soilless mediums you need to ph down to a range of 5,5-5,9 in veg and 5,7-6,2 in flower
Probably you will start to see a few leaf problems by the end of flower week 3 if you don’t start adjusting