Few holes in leaves but no bugs

Hey guys, I have a low pressure setup that works extremely well. I am doing a 15 sec on 10 min off feeding cycle. Using GH 3 part nutes as per bottle for regular veg growth. PPM is at 730 and measured water before and after. Have 4 small plants under a 400w MH 18on 6off cycle. One 12 inch airstone at the bottom of the res filled with about 3 inches of solution. PH is very low 6's. I have one particular plant and ONLY this one plant developing holes in its leaves, it was transported from soil (cleaned very well) and had this issue before hand. The rest were transported from soil as well but this is the only one that has this issue. It also is the fastest grower. There are no gnats bugs or fungus and the roots are damn healthy. I'm attaching some pics to show.

Magnesium deficency... whats your water like and are you using calmag?

I had this problem when i was growing in soil, when i had a lot of rapid growth i had leaves develope with holes but otherwise healthy...took a lot of searching and reading to find an answer because it only seems to show up during periods of rapid growth. You can foliar feed epsom salts, 1 tablespoon per gallon just before lights off or just before lights on. Temps have to be 74 or below for foliar to be effective. Leaves in holes will not get better, new growth will develope without holes. Also a calmag supplement should help. I have found mag deficiency shows around week 2-3 of flowering when the most rapid growth happens from the stretch and thats a good time to boost mag.

Banana444 said:

Temps have to be 74 or below for foliar to be effective.

Click to expand...

Interesting point-----can you please explain why? Seriously, I would to know???

A~~~

Sorry was going off memory, its below 80 to foliar feed effectively

Here, let me show you my stoma!

Thanks for the link----good read-----absorbed through the stoma.

A~~~