Any of the FF soil / soilless products need some sort of lime based additive if the person using those products will actually water their plants properly, (ie; water and feed to 20% runoff, and pot flush monthly, to remove salt build up). So, unlike companies like (Premier Tech Horticulture - Pro Mix, Black Gold, etc, etc), FF products no longer include pH range buffers in their mixes. What I mean... if you pour any water / feed mix holding a pH value greater than those products default pH levels, even something like pH 10, those products will buffer your water / feed mix down to whatever those products adjust their pH too. For example Pro Mix (HP) usually comes in between pH 5.7 to 5.9, then (MP) usually comes in between pH 5.9 to 6.1, and products like Black Gold (Organic) usually comes in between pH 6.2 - 6.4, and their (All Purpose) mix usually comes in between pH 6.3 - 6.5. But with FF products, they may start with a pH buffer of 6.4 to 6.6, but if your water / feed mix is not constantly kept within that same pH range, your soil / soilless mix will soon fall out of its optimal pH range! Which usually results in growers encountering many unnecessary deficiencies and lockouts because while you maybe watering / feeding in the proper pH range, 6.2 to 6.6, your soil / soilless mix is no longer in the proper pH range because those original inadequate starting pH buffering compounds have been flushed away before the grower even begins to flower their plants! So, like I said, if using FF, its best to add some sort of lime based additive to their mixes... (1 tablespoon dolomite lime per 1 gallon of a FF mix (HF, OF), or 2 tablespoons of calcitic lime per 1 gallon of a FF mix (HF, OF), every 5th week during a grow cycle).