Unknown deficiency? Possible rust fungus?

Hello so this is my first time growing autoflowers and long story short I thought I was over feeding them because I got a slight nute burn on the tips of my leaves so I’ve been doing an RO flush to hopefully wash a lot of the salts out in the soil. Now I have these reddish brown spots on my leaves and it seems to be starting on the big leaves first. I haven’t fed nutes in over a week and a half and I can’t do ppm run off tests because I’ve been using DE and it’s been screwing my numbers up so it’s hard to see where I’m at. I ordered some Dolomite lime with a good percentage of cal mag in it so I’m hoping that will help things out. Any ideas or suggestions are greatly appreciated!
FF OF soil
FF trio
Cal mag
Recharge
Top dressed with DE
PH 6.0-6.5

never flush soil with RO
thats why you have calcium def now

kingromano said:

never flush soil with RO
thats why you have calcium def now

Click to expand...

Then what would I flush with?

you never flush
some burnt tips do not mean you need to flush, just to decrease the feed
burnt tips are often caused by bloom nutrients/pk13/14

Yeah I didn’t mean to flush so much, it’s because I wasn’t realizing the DE I put on my soil was increasing ppm readings and I panicked seeing a reading over 3k. So my issue is a calcium deficiency most likely? Would regular cal mag feedings help?

Just go back to regular feeds.

in your case you should flush but not with pure water, with a balanced feed set around 1.5mS
take your plant and water to runoff until your runoff measure 1.5mS
it mean you successfully replaced the old solution with salt accumulated with a new one, balanced and at the right conductivity

If you continue to use RO water then cal-mag have be factored into your feed schedule.

kingromano said:

in your case you should flush but not with pure water, with a balanced feed set around 1.5mS
take your plant and water to runoff until your runoff measure 1.5mS
it mean you successfully replaced the old solution with salt accumulated with a new one, balanced and at the right conductivity

Click to expand...

Gotcha that’s a good idea I appreciate it! definitely gonna do that when my soil dries