Too high for ProMix HP. 6.2 is the top of the safe range for that, so you will need to find a fertilizer like the ones I've mentioned. GrowBig Orchid Fert 20-10-20 is available from Amazon, but like I said, any 20-10-20 fertilizer that is 12% nitrate and 8% ammoniacal nitrogen (or similar percentages) will work.
In the meantime, just feed them.
In the meantime, just feed them.