Growing autos and photoperiod plants together will always present dilemmas.
Either you wait until your autos are finished before going to 12/12, by which time your photo period plants may grow to large for your tent, or you go to 12/12 when your photoperiod plants are at the desired size, however this will affect the maturation of your autos.
Your photo period plants still look quite young/small, so I would wait until they are at least 10-15 nodes tall before going to 12/12, especially if you intend transplanting them into larger pots. If you have no intention/desire to pot them up into larger pots and want to do the whole cycle in those small pots, waiting until they have 6-10 nodes might be your best option.
I wouldn't worry about the purple tips, this can be normal and seeing as your autos are close to half way through flowering, any drastic home remedies will probably do more harm than good.
With any luck, your autos will be harvestable by the time your photoperiod plants are ready to go to 12/12.
Otherwise you will have to decide which plants will potentially suffer. In the future, I would recommend growing all autos or all photoperiod plants at any one time in one tent.
I am sure you will like both Strawberry Glue and French Cookies, they are 2 of my favourites with exceptional flowers, therefore it might be wise to sacrifice some auto quality in favour for these 2 delicious strains from Barneys Farm. In my experience, they will far out perform any auto I have ever grown.
Good luck and happy gardening, whichever way you decide to go.
Hope this helps,......
Organoman.