cute lil guys.... i like the one at the top, is it a crassula??? looks neat regardless... all i can say about keeping them under 24hr light is if they start to look kinda sick for no obvious reason, then take em out for awhile... if not, then enjoy your cacti-weed garden
personaly i would repot each catcus. this way they dont have too fight for root space and can realy take on best growth.
as for brown based one repot carefuly and dont water so much, if you can repot without water see how it goes. maybe a thin toothpick or two will help keep it stable untill it finds its legs again.
I've some Trichocereus Macrogonus that I started from seed that will most likely find a spot in an upcoming indoor garden. I also have several Trichocereus Pachanoi (San Pedro) that are most likely too large to get any floor space under the lights. Both of these are rich in mescaline and legal to grow for ornamental purposes here in the U.S. Three of my Pedros I purchased at my local Lowes. I've also got about a hundred lophophora williamsii seedlings but the indoor lights will be too bright for them so they'll stay on the window sill. I highly recommend growing the trichocereus cactii. Mescaline is a very useful drug at a variety of dosage levels. Lower doses enhance alertness and sociability while also acting as an appetite suppressant and antidepressant. At higher doses it is a wonderful and kind psychedelic experience although very long lasting.
BTW, those little cylinder microdots of years past although sold as mescaline were actually LSD.
I am a cacti / cannabi grower myself. I have a good size cacti garden growing outside not in best sunlight though. Succulents and cacti. My prize and joy is my mother Lophophora williamsii and san pedro with a button I grafted that is growing way expedentially compared to mother. I want to transplant mother into better medium and take more grafts onto my san pedros. Any advice? Substrate? Ph? Nutrients?i want : )