A lot of my babies are browning out, some leaves are literally coming out brown/crisping up before they fully unfurl and I am at a complete loss. This has been happening for the past few months and I've tried everything that the internet tells me to do and I'm still dealing with randomly dead leaves. 
I've been slowly transitioning my plants from soil to LECA because I have a spider mite and fungus gnat infestation (as well as a suspected thrip infestation) and read that they do not thrive in water. I know thrips may not respond since they can reproduce every which way but I drowned my monsteras and giant philodendrons overnight and then coated them in Captain Jack's Dead Bug Brew once they were dry. I'm hoping things start improving on the bug front but grasping at straws rn.
I know some plants do not survive in water super well but I'm mostly waiting for them to grow water roots before I put them in LECA. Most seem to be doing okay, some seem to love it. I also have the GH General Hydroponics FloraGro, FloraBloom, and FloraMicro for when they fully transition to LECA but haven't really used it that much. I don't really know what ratio to use at this point but plan on doing a bit more research. I have my own water distiller and am slowly introducing DI water so I can eliminate tap water as a cause of the issue.
I haven't had this issue in the past and it seems like it's getting worse, especially my poor Tradescantias. I had a beautiful Zebra that crisped up and died within a week for no apparent reason. I saved little bits of it and am trying to prop them, but those are starting to go too. I've done all the things people recommend; insecticidal sprays, repotting, washing, drowning, bonide, mosquito bits, tea tree oil mixtures, you name it, I tried it and nothing is working. What the hell am I doing wrong here??

Not sure why my plants keep browning out...