First grow ever, and it's DWC

Hi, same size tent as my old one, an heat was always a problem unless I left the tent door half unzipped. I can recommend having a fan inside the tent, instead of blowing air from outside in, use your extractor to draw the hot air out otherwise it will just hinder and cause high humidity, especially after watering. Once you have the fan in there and your extractor sucking the hot air out of the tent, whichever room your tent is in, leave that window open.. You'll be surprised how much it helps maintain a steady temperature as the outside of the tent being cool will keep the inside of the tent a good temp. Otherwise the whole room just cooks, had that problem and I really didn't enjoy it! Let me know how it goes and hope it helps you out.

I agree with @Michka, if the solution is at 6, she will recover just fine. One more thing, in about 3 of your photos, the tips of your leaves have browned. I think your nute levels might be a little high. In the past for me, just adding more water helped lower the PPM. Those tips will never go back to fully green, but they won't get worse and all your new leaves will look great. The plant will be fine.