CherryPie (auto) - Blimburn Seeds

You got the taco, Heat/Light stress. Either your temp/humidity is in a bad range( Search "VPD Chart" ) or you have to much light going to the plants. Install a LUX app on your phone and see what the LUX is at the top of your plants. your looking for between 45,000 and 55,000 in veg and 50,000-75,000 in flower. These numbers are approximate and will vary based on your phone and grow lights used. a PAR meter is ideal, but that costs a nice chunk of change. Good luck and Happy Growing

See the leaves looking kind of canoe like. That is a sign of heat stress. Take GGS'S advice, keep that room cooler.

It seems like your other plants have the same issues, wilting leaves. Most likely its because vom temp and humidity. You wrote that you have problems with your AC. I would try to get the climate right, somewhere at 25C (75F - 80F) and closer to 50% - 60% humidity. The plants will grow under your conditions, but there may be some issues to come if you dont correct at some point (Slower growth, lower yield, mold). But for now they will definitely grow. Hard water per se usually (on a small scale grow) is not a big problem. Depends on where you live, but "hard water" just means it contains more calcium and magnesium, which is a good thing for the plants. You want to make sure that if you use tap water (which in my region is very hard, actually the "hardest" in my country - around 300ppm) it doesn*t contain possible harmful elements (suchs as chlorine). You can either call your water supplier and ask for the contents of the water, or you can just send a sample to a water testing lab. TL:DR If you live in a developed country, and you can safely drink your water you use to water your plants, its usually fine. If in doubt, leave the water in an open container for a day, to evaporate any possible chlorine (e.g. as in the US). In your diary it states you water with ph 6.5. If not already done, buy a good ph-pen to accuratly set your ph. in early veg, opt for a little lower ph, like 6.3. Later you can go up to 6.5.