Your Lowes sells Pro-Mix? The ones in my area did a close-out sale over a year ago. (I grabbed 6 bales.). Someone at Lowes told me the distributor was prevented from selling it through consumer big-box retail stores. According to Premier Hort., it's only supposed to be available through specialty nursery shops, hydro stores, etc.6 plants, Jacks Citrus, Epson, Xtreme Mycos, Cheap Lowe's Promix ($14 2.2 cu ft), perlite.
At that time I mentioned it at my local hydro store (HomeGrown Urban Gardening in the Phoenix area). Later I overheard the bitch who managed the store saying she was the one who complained to Premier (or the distributor) and had Lowes shut down. That changed my opinion of the store. They cut back hours, closed a store, she's gone now. But, I rarely buy anything there because of that.
The Lowes in Phoenix sell a Premier Hort. sphagnum peat which is very inexpensive. Doesn't seem to have been treated with dolomite. I've been thinking about trying that with a heavy dose of dolomite, 40% perlite and some Xtreme Kykos to recreate Pro-Mix HP. That would be 1/2 the price of Pro-Mix HP.