You MUST increase your air exchange rate, or add CO2.
Lower pH to the range given by GG.
You are quite leikely overwatering; 7 cycles/day rockwool flood/drain sounds excessive to me. You really would like you medium to get fairly dry between flood cycles. Why did you choose RW for flood/drain? Taht medium is IMHO FAR better suited to a drip system.
Your fertilizer solution could likely use a boost since you are not using it close to the rec. dosage.
Heat spikes into the 90s aren't good.
And depending upon the actual number/size of your plants, you may need a larger res.