Definitely add more full spectrum lighting if you can. 60W is very low. Try and get to at least 100W per plant if you can. You have a very small space so I would suggest only having one plant using LST (google it if you don't know what this is) to keep the canopy at the same height. It's so easy to do, takes no more time and you'll get more nice bud that way, using less seeds, than cramming four plants into a 60cm x 60cm space. They'll compete for light if you do that (which you already don't have a lot of) and grow tall and spindly and won't have decent buds.
You also need to factor in the lack of height in your grow room and make sure your plant(s) are small and fat. They'll get light burn (or worse, too hot!) if they're too close too the lights,
One last piece of advice - don't top your auto. A little LST will be fine but it needs to grow quickly and be the best plant it can be if you want decent buds from it. There's no time for recovery in auto plants. Another good reason to only grow one or two instead of four in that small space!
Good luck and have fun! :)
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