Possible pest issue but unsure. speckled leaves?

Not sure what's going on here. The closest thing I could find online is a bug problem, but I haven't been able to confirm anything as of yet. I was hoping more experienced growers can offer a few suggestions.

I use a 4000 lumen 2 bulb x 2 foot T5HO light, about 3 inches above my plants (only growing 2, and not very tall, so please, no suggestions for better lighting because I don't have the room).

I have them in a DIY grow box currently without ventilation, though I plan to amend that as soon as I can afford it. There's plenty of cracks in the box, and I open it frequently to check on them.

I've been watering them once a week with spring water and filtered water. Burpee pH meter tells me I'm about 6.8-7.0. Sounds like that's not an issue.

I use Roots Organic Original soil, which is what I germinated in as well. The affected plant is also about 2 1/2 weeks old, but has been growing really fast for a T5 grow.

Here's a pic of the whole affected plant:


Ignore the burnt looking lower leaves. That issue seems to be a closed case (transplanting and flushing stopped the spread), though that was only last week.

I do have a 1/2 tsp/gal solution of FF Grow Big, but I was going to wait to start feeding when the soil dries out and is ready for watering. I don't think that would help me with the current dilemma anyway.

I haven't been measuring temp/humidity at all because I really don't have a way to change either one.

Just hoping it's not a pest issue, even though it looks like one. That would be a pain in my ass.

So, what do you all think?

The strain is banana kush, by the way. Got my seeds from a bag (had A LOT, so I only picked the strongest looking ones). Good quality bud, surprisingly, for the number of seeds I ended up with.

You got spider mites...good luck with that, you'll need it.

Something is eating those leaves. Look under the leaves with a magnifying glass.

You need a 30X magnifying scope to look closely for bugs but it kind of looks like thripes...........look under the bad leaves for eggs (if so, then it is mites).

a cheap solution for mites. Fill a spray bottle with water, add a couple drops of dawn dish soap, drench your plants several times a day. Its not a final solution, but gets the job done. It washes them off the plants and drowns the little buggers. The eggs will still hatch and they will return, so keep at it until ya can afford a more violent method. If you can afford it get Mighty Wash. It kills them dead.

Figured as much. Ill probably just grab whatever they have at lowes cause the nearest hydro store is a good half hour away, an I have very little cash.