unknown plant problem. need help urgently.

i have some plants 3 weeks into flowering. they all have looked really great up until the other day i noticed small redish/brown specs all over a few of my leaves...looks like someone took a pen and went . . . .. . . . ... . all over the place.

barely visable until you get right into the plant...

problem seems to be worst on 2 of 5 plants...mostly around the middle of the plant. not showing any other signs of problems.

nutes: fox farm soil and nute trio.
temps: around 70-75 in the day...as low as 67 at night.
watered twice per week (i always have watered twice per week...i use 5 gallon pots)

here are a few pics. it looks kinda like a calcium issue based on a pic i found online but it only appears that way up close...i notice sometimes the red spots concentrate around the veins of the leaves...which led me to think buds were in there but after using a scope i didnt see any...and yes i checked the undersides of leaves...no thrips or spidermites (that i can tell).

i checked on them today and the issue may have spread a litle but its minimal at best at this point so HOPING its not bugs because i'd figure it would spread by now.

in fact one plant has the worst of it the second in comparison isnt that bad...

heres some pics (including the 1 i found online that looks most similar to my problem but doesn match 100%)

 

i don't have a way currently to check ppm...however my Ph between all the plants has been decently stable in the area of 6.5...give or take (slight fluctuations).

i only feed once a week the second time is just plain water...my waterings are spaced out evenly. I'm sure its not over/under watering as the problem is only on 2 plants really..this is what made me think its not bugs as it would have spread (i noticed this 2 days ago but haven't been able to diagnose it).

i seen a similar pic like mine on another forum but no one there had any advice and the poster never came back to say if he got rid of the problem or if his plant died etc. so i have no idea what I'm up against.

i did use spinosad just in case it was bugs and i missed (had thrips earlier in the grow..minor outbreak...maybe 20 or so between all 5 of them...caught it early...only the lowest leaves were touched)

sorry about the pics its the best i can do right now.

if you look closely you can see the tiny spots everywhere and i don't foliar feed (so its not the water acting like a magnifying glass)...granted the spinosad was foliar fed but only at lights out...so it has a full 12 hrs to dry/recover.

so i doubt its that either...i really just don't know what it is...