Rust spotted leaves and curling with pics

I am a first time grower, with 3 plants that I didn't know any better, and started with flourescent tube light too far away, and about 8/16 from time of planting to about 10 weeks when I took them outside, which is why they are small and scraggly.
At least I got lucky, and of all the seeds I planted, these three females were all that got saved when I started thinning them and transplanted.
At 14 weeks, the largest of them started getting rusty spots on only the larger leaves mid height.
Somebody looked at a pic of them, and suggested it was a cal/mag deficiency (I have them in Miracle Grow soil, with the Miracle Grow plant spikes that are 6-12-6, and before that, used to fertilize once a week with M/G general purpose ferts. that are 24-8-16)
Now, I know there are mixed opinions of Miracle Grow, but that is what I had, and I really didn't plan on the plants to last this long or do this well, but after seeing them progress like this, I am getting more and more anxious to see how well I can do, and what I can get at harvest time.
When I was told it was a cal/mag deficiency, I started spraying with epsom salts and also started putting some eggshells on top of the soil.
The spots stopped for about a week, but now are back worse than ever, and are starting to come out all over and on the smaller leaves as well.
Just a couple days ago, I checked my tap water that I let sit out for 24 hrs for them, and the PH was up over 7.8, so yesterday when I watered, I added vinegar to bring the PH down to 6.6
I'm kinda puzzled at this time, since only one of the three plants is doing this, and all get the same light, temp, feeding etc. - Was my problem misdiagnosed, did I try to fix it the wrong way (I'm on a limited budget), or do I need to increase the frequency of spraying and amount of shells?
If I leave the leaves long enough, they will get worse than the picture and really get dry and crispy.
Also, I don't know if this is relevant, but every couple days or so, I am finding these opaque rubbery balls about the size of a ball point pen tip laying on top of the soil and I can't figure out what they are.
Any opinions/suggestions please?

Its not a cal/mag def its just a calcium deficiency. It's probably not from the ph of the soil because calcium absorbs well in higher phs. Though 7.8 is too high. Dolomite lime available all over will help fix a calcium def. Its just has a slow absorption process tho so its not an instant fix. I think you can foliar feed with it too tho to speed it up.

1 tablespoon epsom salts (magnesium sulfate) to one gallon water one time. Magnesium deficiency is at least part of the problem. They go together (Mg+ & Ca+) ion-wise to balance. The SO4 chain in Epsomite helps balance pH down but not a lot. It does help. Slight acidification of soil helps speed decomposition of organic materials in your soil so they can be used by the plant easily.

I agree with bostoner. You could also use epsom salts in your water or foliar feed with it but if you decide to go foliar feeding route you want to test your mixture on one leaf first and see how it responds before you treat your whole plant.

calicat said:

if you decide to go foliar feeding route you want to test your mixture on one leaf first and see how it respondes before you treat your whole plant.

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Amen to that!!!! Ground eggshells are a good source of readily available calcium. The finer the grind the faster the uptake. Bone meal as well. Or a slam of good nutrients!

Great! Thanks guys,It sounds like I should keep up with the epsom salt, to keep the PH from increasing, and also continue with the eggshells to increase the calcium.
Glad to hear I didn't hurt them