cal mag deficiency...what to do?

I have one plant with what appears to be more of a calcium deficiency and another that seems to be having a magnesium deficiency. After I catch the water out of the bottom of my pots it reads at about a 5.1 Ph. The water going in has a Ph of about 7. I have been feeding it General Organics Cal/Mag for the past week. It seems to have stopped the yellowing on the plant with the red/ brown spots but the spots keep appearing. The other plant is starting to yellow on a few leaves like the one pictured. Both are in super soil. If it makes a difference I have a third plant in the same soil looking great. Please help! Thanks!

I should add that the temps are around 79, 400w HPS, Day 25 flower.

Try flushing in case there's any salt build up in the soil. Hope they get better so u get strong healthy dense flowers

Kelp meal and Epsom salt

General Organics Cal/Mag is a very good product. Flush and give it a bit of time to recover. As mentioned above, Epson Salts is also a readily available and much less expensive cal-mag treatment.

As for kelp, I use it everywhere. I buy water soluble kelp powder and add it to my watering and foliar feeding program. Kelp is especially effective when foliar fed. You may try some foliar kelp spray program to give those sickly plants a big boost.

If you read the ingredients on the bottles, a good number of bottled nutes are mainly kelp with lots of water added. Some are supplemented with Humic Acid (Liquid Karma). I make all my own solution using powdered, water soluble nutes rather than paying $$$$$$ for "magical" bottled solutions that are mainly dissolved kelp and other readily available, affordable nute powders. I get mine at Kelp4less, but there are lots of sources...even eBay.