My plants have dark veins and one of em is crispy

Hello there friend. So it looks to me like a little bit of a magnesium deficiency. You can wait until your next feeding or you can make a foliar spray with a little epsom salt. You want to keep your solution to under 200 PPM and at a balanced PH of 6.3-6.5. I see you said you are waiting on getting that PH meter. Definitely a good investment. Also get yourself a TDS meter if you don’t already have one. Very important tools to have. Your plants are looking really nice though. Keep it up and you’ll get there my friend. 🤙