Basically for an "emergency" like this, your goal should be to simply keep his shit from dying, not growing dank ass bud (that's his job)...
so I suggest check the PH and PPM once a day. Add up/down as needed to maintain 5.5 - 6.5 ph, although try not to go over 6.0 too much as phosphorus lockout can occur which would be very bad during flower. 5.8 is perfect.
If he is running ice in the reservoir to keep temps down, you're gonna have to replace the ice. Try to keep the water around 62-70* F
Probably keep the PPM at whatever it currently is. If it gets higher, your plants are drinking water and not using nutes, so add more water. If the PPM goes lower they are using nutes and not drinking as much water, so add nutes. You want to use the Flora Bloom and Flora Micro, I wouldn't recommend fuckin with the bloom booster and other additives unless you have problems, then ask us first. Keep in mind if there's already shit in your water or ph up/down or other additives in the nute solution it will increase the PPM. For example: you might have 1600 but 400 of that may be from tap water, ph down, and additives, so you only have 1200 PPM of actual nutes.
To be safe, say on the low side of the PPM guidelines and watch the plants for dead/brown burn spots at the tips, black or deep purple/brown spots on the leaves, excessive yellowing of the leaves (if he is close to harvest they are probably yellowing a bit), and wilting/drooping. Other than checking the PH and PPM once a day, just watch the plants and post pics if you see anything unusual. DWC pretty much runs itself once properly setup.
As for your 24/0 photoperiod plants, those are probably clones. Most likely all you need to do is: If they are clones in a humidity dome, keep the inside of the dome misted and leave them alone otherwise. You may need to ensure the rockwool or whatever medium they are in stays wet (not soaked as fuck).
If they are clones or have a pair or two of three-fingered leaves, ONLY IF YOU NOTICE THEM DROOPING OR YELLOWING ETC feed them a mild nute solution (I would go half of what the schedule recommends for his clones to be on the safe side.)
In general, your priorities should be keeping the flowering plants alive, and then worry about the clones/seedlings. If you lose the clones, he can get more. Watch the plants and ask questions (with pictures attached) if you have any further issues. Also, you might want to pop open the res or buckets every meow and then to make sure everything is cool and you're not growing The Swamp Thing in your res.