HELP! Requesting Help on How to Recover from Believed Nutrient Burn

[Subliime93]

This is my first grow, it was going well at first but I ran into issues. I tend to be long-winded, I'll try to be succinct but also want to provide adequate detail. The plant is a Northern Lights auto flower and I was following a light/nutrient schedule I found online (supposedly specifically for auto-flowers) and using Fox Farm trio nutrients per gal of water.
-6/19/22 (week 3) 1ml Grow Big, 2ml Big Bloom, no issues yet.
-6/21/22 (week 3) Flushed with just water but forgot to check/correct my pH.
-6/22/22 (week 3) Noticed it has some very small light-tipped leaves all over, looked on this site and assumed it was pH fluctuations so still fed it 1ml Grow Big, 2ml Big Bloom.
-6/23/22 (week 4) Dry already (cloth pot with a fan on high), the schedule I use said flush every 3rd watering so I fed it the recommended 2ml Grow Big and 4ml Big Bloom.
-6/25/22 (week 5) Flush, tips were still there but didn't seem significantly worse and I raid once there are issues the leaves don't really "recover" so still thought it was the original pH concern at this point.
-6/26/22 (week 5) Soil was dry so fed it again, 3ml Grow Big, 6ml Big Bloom. But it looked like the tips worsened which had me concerned it was actually nutrient burn... but I was still trusting my online source at this point. Also noticed some small brownish spots in the middle of one or two leaves. Not drooping/sagging at all so didn't think it was watering. Did buy/start adding cal-mag in case it was a calcium deficiency.
-6/27/22 (week 5) Fed 3ml Grow Big, 6ml Big Bloom.
-6/29/22 (week 5) Realize it's probably nutrient burn at this point because it worsened so I just flushed it.
-7/1/22 (week 6) flushed it, but did add 2ml cal-mag because I heard it's hard to overdo that in case it really was a calcium deficiency. Also noticed first pistils.
-7/3/22 (week 6) Baby buds starting to grow so I wanted to feed it but did one less ml than suggested for every nutrient, so 3ml Grow Big, 5ml Big Bloom, and 1ml Tiger Bloom.
-7/5/22 (week 6) Nutrient burn looks like it got worse, just flushed it.
-7/6/22 (week 6) Flush.

Next watering I was planning on dialing back the suggested amount even more to 2ml Grow Big, 4ml Big Bloom, and 1ml Tiger Bloom... is that still too much? Do you think my plant will survive based on the pictures and any advice regarding a nutrient feeding schedule?

[3Berries]

If you are in flower and the runoff pH is below 6 you can flush with water till the cows come home and it will stay there. All the nutes and CalMag minerals are what is driving this. When saturated with minerals the pH really fluctuates when the medium dries out going low. Adding any extra nutes will not make things better. Welcome to my world. But I have a plan that seems to be working.

And that is overdosing my water with Magnesium Carbonate, up to 3 grams to a gallon. This will not dissolve for the most part, depends on the initial water pH. But it will react with the low pH minerals in the medium. And it will flush out.

I currently have a girl at 9 weeks in flower that has been constantly low pH of under 6.0 for the runoff. It is showing nute burn on the tips and yellowing, not taking up nitrogen. The last week I have been using the MgCO3 mix and the pH last night was 6.4 in the run off. It gets watered about every other day. This plant is the last of my extra calcium experiments.

I do add extra perlite to my soil mixes so it forces me to water more frequently. And it also make me realize that the Ca and Mg carbonates in my well water are a blessing. I've been using rain water but will now use a mix of well, rain and a pinch of the MgCO3 per gallon as my base water.

[Subliime93]

I'm new to this so sorry if this is a dumb question, but I pH correct my water after adding the nutrients, that doesn't prevent what you're talking about? I guess I don't understand why my runoff water would have a low pH.

[3Berries]

As the soil dries out the minerals not used up become more concentrated. The more concentrated the more acidic or lower pH. Just like boiling anything down to reduce volume.

And then there is the soil ingredients and microbe action.