I believe I have a magnesium deffiency,the leaves on my plany mostly the fan leaves as well as other new growth have turned almost a yellow!.... I grow with sultz potting soil/mixed with half perlite my PH is around 6.8 I don't believe it's a lack of N simply because I am only one week into flowering and up to this point all the plants were really a nice forest green! which could only mean lots of N now several of the plants have yellow leaves,I should also add I don't believe the fan leaves are turning yellow because of the sugars being sucked out by the plants simply because they ain't that far into flowering only a week and a couple of days................now my ph was below 6.5 for several days which might have locked out magnesium uptake but I'm not sure!.......so I went out and bought some epsom salt to increase the magnesium and was wondering how much epsom salt to mix with five gallons of water?.....................and how should I go about fixing the problem? Should I flush the plants with ph balanced water then add epsom salt Or should I mix up ph balanced water with epsom salt?...... I was also wondering just say if my ph was to low for a couple of days which prevented the plants from taking in magnesium,and if I am right about it being low ph locking out the magnesium and I add epsom salt will this possibly lock out the iron?...........I was reading something somewhere if your soil has to much magnesium somehow the iron gets locked out because of the magnesium...................... Anyhow guys anyone with some niffty idea's on how to cure the problem? which way and what approach should I take on this,this is my 5th grow and it is the best grow yet for me to date! everything is running so perfect even advanced and moved on up in the world with advance nutes,just hate to have things effect this grow.........the last 2 of my grows lost most of their fan leaves and secondary leaves before the plant finished flowering!.... The Pic below is showing a light green colour leave which use to be really dark green,I have other leaves that are even more yellow! am I correct with my guess or is this a entirely different problem then magnesium deffiency... Thanking you in advance..