It sounds to me like your MS is way too high for use under a 250 watt. If you want to use higher fertilizer concentrations, you need a larger light. Under the 250, try cutting your nutrient level back by about 33-50 percent. You should notice a marked improvement.

Also, nutrients build up in rockwool over time, so your nutrient level may be much higher in the cube or slab than what you are running in the tank... squeeze some nutrient from a cube or extract from the slab with a turkey baster and test that nutrient level independently. If it's higher than your tank MS, you've got a build-up problem and you need to flush with plain water, dump all of your old nutrient and replace with a more diluted solution.

Let me know if this helps.

Harvestmaster

Upward curl on the older leaves can be due to Mg deficiency. Cupping on older leaves that progresses to the younger leaves can be due to Mo deficiency.