Congratulations on expecting and best of luck with the new house my man, hopefully it all works out for you!
If you can't afford a pH meter, you can do without one but it will be a little more difficult on you. Yeah, I see a slight touch of nute burn but not bad at all. No worries on that. I don't really see any signs of deficiency, that is good, so my guess is your pH may be off a little. Not too bad because the leaves still look pretty nice with the exception of a little twisting, like you said. It is hard to know exactly without a good test. You are using promix, which has a tendency to stay alkaline early. I have used it for years now and that is normal for me as well. There isn't a lot you can do without correcting the water with phosphoric acid but without some of way testing the pH I wouldn't recommend that at all.
So, right now, not seeing any deficiencies and knowing we have a little nute burn, I would continue to water with your RO for the remainder of the week and see how she grows through it. Once the roots get well established, they will help correct the pH by their exudates. Things still look pretty good overall.