*First Grow, need diagnosis please?

*Hello all, thank you in advance. This is my first grow and i'm getting speckled brown spots on my fan leaves and they eventually turn yellow. see some red veins too. I've got two plants (bubble kush and blue cheese) in closet in FF ocean in 5 gal buckets with drainage (both plants affected). Both plants otherwise appear to be growing healthily.

Wasn't feeding too much (light FF Grow Big during veg) when it started because they were growing too fast and thought FF had adequate nutes, so don't think its nute burn (but could be wrong i guess).

Right now they're 20 days into bloom.

I water about every 5 days.

Temps been in low 80s, 50% humidity.

Havent checked ph in awhile because my ph tester doesnt seem to be working (new one coming any day now) but earlier in grow was around 5.5 with all same conditions.

Under 2 led 90w ufos (so its not heat).

1st thought mites, but never seen anything living (with microscope, magnify glass) and think would see webs by now, been going on for weeks.

Next thought magnesium deficiency cause of red veins, gave good strong feeding of FF tiger bloom 5 days ago (has mag) but problem still getting worse. May try epsom salts next?

I've been looking at different pictures/videos and reading everything i can find but I'm getting to the point everything i read seems to fit my problems and i don't want to start trying everything all at once to fix it.
Any advice for a lost amateur? (also this is my first post, if i'm doing anything stupid please let me know, thanks)

And a couple things i forgot to mention...

Yellowing starts in center of leaf blades, not on tips. And long after many brown spots cover leaf.

Brown spots started slowly showing about 3 weeks into veg i think. (i started bloom too late, after bout 6 weeks of veg, rookie mistake, they're too big!)

Calcium (Ca) -Macro Nutrient and an Immobile element.

Calcium is another important element that helps the plants cell walls, cell division in making the plants stems, stalks, branches stronger, as well as contributing to root growth, mostly the newer root hairs, Calcium also helps enhancing the uptake of K in the the plants roots. Calcium moves really slow within the plant and tends to concentrate in roots and older growth.



When plants exhibit a Calcium deficiency the younger leaves are the first to show it as well as older leaves. The Leaf tips will die back, the tips may curl, and growth of the plant is stunted. The plant can show a weakness in the stems and branches, as well as a under developed root system that can lead to bacteria problems with roots dieing off. Having slow plant transpiration rates can aggravate the uptake of calcium. Make sure your soil isn’t very acidic, for calcium gets harder to be absorbed through acidic soils, Which leads to having a plant that is deficient in Calcium. The leaf tips, edges and new growth will or may turn a yellow/brown color that happen in spots and often surrounded by a sharp brown outlined edge and then the leaf tips die back. If too much calcium is given at an early stage of growth it can stunt the growth of your plants. Having to much of calcium will also flocculate when a concentrated form is combined with potassium. The parts affected by a calcium deficiency are the roots. Stem or petiole, young or old leaves.

Too much Calcium will lead to other micronutrient deficiencies. Calcium fixation is caused by many types of mediums such as: clay soils, unbuffered coco and humus. The lime tends to bond to these soils very easily. The stems of the plant will not be able to hold the plant up and will exhibit a white brown in between the veins of the leaves when having too much calcium. Also having to much potassium and or nitrogen will cause a calcium lockout.



Problems with Calcium being locked out by PH troubles

Very acidic soils with excessive potassium, dry and or wet soil. Lack of calcium in the soil may cause too acidic soil. This may cause to Mg or Iron deficiency or very slow stunted growth


Soil


Calcium gets locked out of soil growing at ph levels of 2.0- 6.4
Calcium is absorbed best in soil at a ph level of 6.5-9.1 (Wouldn’t recommend having a ph of over 7.0 in soil) anything out of the ranges listed will contribute to a
Calcium Deficiency.


Hydro and Soil less Mediums

Calcium gets locked out of Hydro and Soil less Mediums at ph levels of 2.0- 5.3
Calcium is absorbed best in Hydro and Soil less Mediums at ph levels of 5.4-5.8 (Wouldn’t recommend having a ph over 6.5 in hydro and soil less mediums.) Best range for hydro and soil less mediums is 5.0 to 6.0. Anything out of the ranges listed will contribute to a Calcium Deficiency.




Solution to fixing a Calcium deficiency
To fix a calcium deficiency you can treat by foliar feeding with one teaspoon of dolomite lime or Garden lime per quart of water, Or Any Chemical/Organic nutrients that have Calcium in them will fix a Calcium deficiency. (Only mixing at ½ strength when using chemical nutrients or it will cause nutrient burn!)
Or you can take crushed up dolomite lime or garden lime in a gallon of water and water it in the soil. 1 to 2 teaspoons per gallon of water, which will be slow acting. Garden Gypsum, which is medium absorption. Limestone, which is medium absorption, Rock Phosphate and Animal wastes which are both medium/slow absorption. Note: Caution when using gypsum to an already acid soil (pH that is less than 5.5) can have a very bad effect on different types of plants by effecting the absorption of soil aluminum, which is poison to plant roots.

Thanks Bloomin! Will wait till my new ph tester comes then probably try the garden lime after specifying my ph levels so i know exactly what i'm dealing with