havent been watering enough

I realized that I haven't been using enough water. The plants are in 7 gallon pots and I've been giving them 1 gallon every couple of days. This started to cause some problems a few weeks ago when I noticed Mg deficiency. I'm not noticing phosphorous deficiency now and I think there may be a nute lockout problem from the watering schedule. Good news is that I realized my mistake and I'm giving them 2 gallons every few days now. Other good news is that I'm not using chemical fertilizers, I composted the soil myself for 1-2 months before planting.
I'm concerned about the salt buildup, which I think is causing the nute lockout. I don't want to flush my soil because I will lose all of the beneficial microbes that are in there. Whats the best thing I can do at this point?
 
Thanks

 

bump, anyone have an idea?

 

here they are. you can also see more pictures in the journal


 
im a little worried about the discoloration in the leaves on this top.

 
its a pretty simple question though i think. i havent been using enough water to flush out accumulated salts during regular waterings (only 1 gallon for a 7 gallon pot). i understand that flushing the soil and then adding a mixture of medium strength nutes is what a grower that uses chemicals should do. however i have organic soil and dont want to flush the essential microbes out of the soil. so my question, is there anything i can do?

 

thanks for the help. its well water filtered through an RODI unit so its pretty much pure h2o.
in that case i think im going to run 7 gallons through just to be safe.
do i need to worry about replacing nutrients though?