first post technically second grow. need a bit of help please!

so this is my first post on rollitup! Hello everyone! Althought I've been on here for a few years reasearching and reading on and off. Hopefully this is the right place to post this? Idk if this is a beginner grow section or not. Never posted on any forums before so hopefully I got it right! ANYWAYS so I got a world of seeds strawberry blue going and a seedsman afghani #1 both have just been transplanted into 3 gal geopots filled with ffof, happy frog, and perlite. The afghani seems to be doing great where as the strawberry had these rusty brown splotches before transplant and now have turned into brown spoltches with the leaf tips pointing up. From what I've read it seems to be mg defiecient. Or a lockout. I have ph up and down and a color panel test kit but I honestly do not understand anything about how to change soil ph or what the in and runoff ph tells me so I've just been watering with 7ish ph tap water. Although a few times I put a drop of ph down once but it only changed it to about a 6.8 so yaaaa. Basically I have a lot of questions that I cant seem to understand without first handed asking. Please get back to me

whats the temp in the room

before the transplant it was a steady 73-79 now with the extra lights its about a 75-81

pictures would be helpful

Pics will help but here are the basics of ph up and down.

Since youre in soil you want to aim for a ph of around 6.5 in your water and nutrient solutions before you water your plants. Have your water handy it really helps if you have a pipette to add the ph down you can measure how many ml youre putting in at once. For example in 1 gallon of water for me it takes around 4ml of ph down to get to a ph 6.2-6.5 then i water. If you dont have a pipette or ml measuring device 5ml is 1 teaspoon.

Add 1 ml at a time if you are unsure how far it will drop. Swish your water around for a few seconds to mix it in dont shake it like crazy just a light mix is fine. Measure your new ph. If you need lower add more ph down and rinse off your testing apparatus and test again.

With a little bit of experience you will get to know just about how much you need to add to get your ph where you want it.

I saw youre using FFOF its good stuff. If you can find a Fox Farms feeding schedule on the back page there is a chart showing how well plants absorb nutrients based on the ph. Dont worry about your soil ph level just adjust your water.

1 last thing if you are letting your water sit for a long time before watering test your ph again because as water sits the oh will naturally rise over time. Same as with pools and hot tubs im a maintenance engineer and we use acid pumps with a constant stream to maintain ph. So if its been sitting for 4 hours or more test it before you water. Hope this helps.