Tiny yellow spots on very young plant

[Lily Flower]

Strain: THC Bomb
Type: Hybrid Indica 65%/Sativa 35%
Number of plants: 3
Stage: Vegetative
Age: 18 days from germination/seed
Grow Medium: Soil
Soil Mix: Espoma Organic potting mix; nothing else
Pot size: 3.25in/8cm
Light Configuration: 3x 65w (350w eq) CLF; 2x 6500K 1x 2700K
Air Circulation: Occasionally; not full time. exhaust and intake set up, but I sometimes leave the tent open and just have the fan on. Air moving roughly 40% of the day
Temperature: 73~80
RH: Still in nursery dome most of the time running between 50% humidity with dome off and fan blowing and 70% with dome on
PH of Medium: Unsure
Pests Issues: None
Watering Schedule: Every other day. The top layer of soil looks and feels dry every time I water
Type and Strength of Fertilizers: None; too young for ferts?
Size of Room: 2' deep x 4' wide x 6' tall

So I'm super new at this with no experience. I'm not even sure if there's anything wrong? but I'd like to check to make sure before something goes terribly wrong, if anyone doesn't mind helping a newbie. I've been taking photos almost everyday tracking the growth. I considered doing a grow journal, but I dunno if I'm really up for it ._.

Here are the pics from just earlier~ I only just noticed the spots today.
first one is just an overall shot

second one shows the spots more clearly

I'm also concerned about the yellowing on the edge too. I'm not even sure if this plant is old enough for fertilizer? Or maybe she is? But she's still pretty small I think? I mean it kind of seems like a deficiency problem? But I'd love a second opinion before I start feeding her any ferts.

I have some weird brand "Monty's" 4-15-12 at the house, but my local gardening store carries multiple fox farm fertilizers, so I don't mind a small trip out to pick up some. I'm also thinking maybe it's time to transplant her into a bigger pot. I'm thinking maybe 3 gallon smart pot to give her more room for roots to grow before starting ferts?

Any advice, insights, suggestions, comments, and/or criticism will be appreciated!

Thank you so much!

 

[Peripatera]

I think it's ph lockout your plant cannot absorb nutrients from soil flush your plant with clean ph 6.5 water and if you dont have ph down use lemon juice too ph down your water.

 

[Lily Flower]

Oh okay. I thought about getting a ph tester, but I'm not sure which one to go with. Any suggestions?

I also studied the picture a little more and got really scared that the white stuff might actually be webbing from spider mites; cause apparently small yellow spots COULD be a pest problem (I have a few random plants that I brought in to my tent, so it's not just my three girls; can't completely rule out whether or not they brought pests in). But I've checked EVERYWHERE in my tent and haven't noticed anything aside from the occasional fruit fly that hovers around. I decided to spray down the tent and everything last night with a neem oil solution.

Everything seems fine so far. No further damage, so that's a good sign, right? Do you think she's at a stage where I can start feeding her nutrients after I fix the ph issue? She still seems a bit young. I dunno though; I feel like I just wanna baby my plants. They're growing up so fast.

Also thinking about investing in a digital microscope. Any suggestions for that as well?

 

[Peripatera]

Spots on leaf is calcium deficiency ? = high ph.

 

[Lily Flower]

Thanks Ichijava~

I just took closer up pics of the damaged spots, but again, nothing new, just old stuff


I'm not sure if the cotyledons are even an issue at the moment, but I see it on all three plants. The yellow pinhole spots are only on the first real node leaves of only one plant. But yeah, nothing on the new leaves at the moment is a huge relief.

I'll mix a little bit of lemon juice in my next watering.
Again, if anyone has recommendations on a PH tester, I'd love to hear it!