Improvements and advice

AC does the same job as a dehumidifier and it also cools. Could just rely on the AC unit alone unless its getting to cold. then get a small dehumidifier. I don't worry about RH unless its 65-70%+ to much engery wasted to keep a plant happy.

Your setup looks similar to what you're gonna see in a section of a mass grow. I suspect you've either worked in a facility or at least copied the layout of someone who has. More doesn't always equal better though as you've discovered with the PM/Budrot issues you've had in your last grow. In my opinion your biggest problem is airflow and microenvironments. You could safely cut your plant numbers down by 1/3 or even by half and just train out the plants more to fill canopy space. I also don't think you're moving enough air through your environment. More fans inside your growspace and more/better exhaust or ditch the exhaust and run a closed system with CO2, in which case yeah get a good dehumidifier and AC. You run into more heat/humidity issues in a closed system though so exhaust might be simpler.